PDA

View Full Version : Octane Mixup


Valentine One Radar Detector

ChevyMan
01-25-2008, 09:20 PM
I wanted to refill my Chevy tank with Regular as usual but somehow inadvertently picked up the wrong nozzle and put $35 worth of Plus before realizing my mistake. Price for PLUS is 10 cents a gal. more than REGULAR. I know it won't harm the carb or any other engine components BUT, what benefits would they ..carb, etc...gain?. Could be just my imagination but it seems to be easier to start a cold engine unlike before the "mixup" ;D

Eric
01-25-2008, 09:24 PM
I wanted to refill my Chevy tank with Regular as usual but somehow inadvertently picked up the wrong nozzle and put $35 worth of Plus before realizing my mistake. Price for PLUS is 10 cents a gal. more than REGULAR. I know it won't harm the carb or any other engine components BUT, what benefits would they ..carb, etc...gain?. Could be just my imagination but it seems to be easier to start a cold engine unlike before the "mixup" ;D


With an older, higher mileage engine, you may notice a slight improvement in performance and economy... the reason's simple: Carbon has accumulated on your piston crowns, increasing the effective compression ratio slightly; thus, the engine may actaully "need" the slightly higher octane fuel to operate at peak efficiency... also, with some brands, the more expensive grades might have more than the minimum detergent/additive package - and that could account for the smoother running, etc.

DonTom
01-26-2008, 05:26 AM
"With an older, higher mileage engine"

Wasn't the octane ratings for regular higher in the 1960's /70's? I forgot what year his car is, but perhaps the higher grades of gasoline today are about the same as the lower grades back in those days.

-Don-

Eric
01-26-2008, 06:14 AM
"With an older, higher mileage engine"

Wasn't the octane ratings for regular higher in the 1960's /70's? I forgot what year his car is, but perhaps the higher grades of gasoline today are about the same as the lower grades back in those days.

-Don-


His car's a '77 (as I recall) so it was designed to use "regular unleaded" - which is pretty much the same now as it was in those days, octane-wise...

Engines from the '60s and before catalytic converters (1975), especially high-performance ones, required both higher octane and lead.

DonTom
01-26-2008, 03:25 PM
"required both higher octane and lead."

That reminds me of what happened with BMW motorcycles when unleaded gas came out. BMW made replacement valves designed for the unleaded gasoline. But after many people installed them, it was discovered that the older valves held up fine, but the new stainless steel ones would crap out in no time.
-Don-

ChevyMan
01-26-2008, 04:26 PM
Eric,

***with an older, higher mileage engine, you may notice a slight improvement in performance and economy***

Paying 10 cents a gallon more over REGULAR, I guess the adage "you get what you pay for" appropriately applies in this situation..???. Incidentally, it's a one-owner '76 Impala coupe with slightly over 52K on the odo.

Eric
01-26-2008, 04:48 PM
Eric,

***with an older, higher mileage engine, you may notice a slight improvement in performance and economy***

Paying 10 cents a gallon more over REGULAR, I guess the adage "you get what you pay for" appropriately applies in this situation..???. Incidentally, it's a one-owner '76 Impala coupe with slightly over 52K on the odo.


Wow - 52k? A creampuff! That is very low mileage for a 32 year old car. It should be fine for years to come. You do probably have some carbon build-up on the pistons; this is nothing to worry about, though - and if you wanted to, there are shops that can clean the internals via a solvent that is fed into the engine via a machine for just that purpose...

grouch
01-27-2008, 08:25 AM
Putting a higher octane fuel in a gasoline engine won't do much but lose a bit of performance that you might never notice missing anyway. The octane rating is just how slow the fuel burns. On a high compression engine you want a higher octane rating so it doesn't pre-ignite. The two (or more) resulting flame fronts meeting are what make that sound like pebbles rattling in a tin can. Now, put too low an octane and you do actual damage to the engine on a non-computerized engine and lose mucho performance on a computer engine. I've pulled the heads off an engine that finally failed and the owner had run 87 but it called for 91 or higher. The piston heads and the combustion chamber looked like a jack hammer had been used on them. Lots of little dings all over the place. The engine failed when one of them hammered through the head gasket. That engine was a screamer after I rebuilt it with extra thick gaskets on the head to lower compression just a skosh. ;D

ChevyMan
01-27-2008, 05:45 PM
Putting a higher octane fuel in a gasoline engine won't do much but lose a bit of performance that you might never notice missing anyway. The octane rating is just how slow the fuel burns. On a high compression engine you want a higher octane rating so it doesn't pre-ignite. The two (or more) resulting flame fronts meeting are what make that sound like pebbles rattling in a tin can. Now, put too low an octane and you do actual damage to the engine on a non-computerized engine and lose mucho performance on a computer engine. I've pulled the heads off an engine that finally failed and the owner had run 87 but it called for 91 or higher. The piston heads and the combustion chamber looked like a jack hammer had been used on them. Lots of little dings all over the place. The engine failed when one of them hammered through the head gasket. That engine was a screamer after I rebuilt it with extra thick gaskets on the head to lower compression just a skosh. ;D


Well, since I'm a very slower driver (usually at least 10 mph below the posted limit and staying in the right lane most of the time)for these past 30 plus years, I just might upgrade from 87 to 89 from now on.I know it will be a money well spent. "You can't take it with you" you know! <g>

Larry T

Eric
01-28-2008, 06:33 AM
Putting a higher octane fuel in a gasoline engine won't do much but lose a bit of performance that you might never notice missing anyway. The octane rating is just how slow the fuel burns. On a high compression engine you want a higher octane rating so it doesn't pre-ignite. The two (or more) resulting flame fronts meeting are what make that sound like pebbles rattling in a tin can. Now, put too low an octane and you do actual damage to the engine on a non-computerized engine and lose mucho performance on a computer engine. I've pulled the heads off an engine that finally failed and the owner had run 87 but it called for 91 or higher. The piston heads and the combustion chamber looked like a jack hammer had been used on them. Lots of little dings all over the place. The engine failed when one of them hammered through the head gasket. That engine was a screamer after I rebuilt it with extra thick gaskets on the head to lower compression just a skosh. ;D


Well, since I'm a very slower driver (usually at least 10 mph below the posted limit and staying in the right lane most of the time)for these past 30 plus years, I just might upgrade from 87 to 89 from now on.I know it will be a money well spent. "You can't take it with you" you know! <g>

Larry T


I didn't realize until you mentioned it how lightly used your car is; I had assumed it would be a high-miles car, given the year/age, etc. But less than 60k is really something. You probably have one of the lowest-mileage '70s-era Malibus in the country...

Is the body/interior in good shape?

ChevyMan
01-28-2008, 03:14 PM
Eric,it's Impala, not Malibu which I drive.
I was thinking of selling it while it still is in operable condition and get my hands on another car in the new Millennium range, my reasoning is that if I were able to drive it until I no longer is able to find replacement parts for it, then I wouldn't be able to dispose of it and must junk it. But any dependable car would cost anywhere between 10k and 18 or 20k, and with that money I can do any repairs or maintenance on the Impala and I would be way ahead money-wise.
The body/frame is in fine condition, of course, with rust spots here and there especially lower parts of the doors. It still have the original factory paint job albeit with rusty flat surfaces...roof, hood and trunk...which I treat with 3-monthly wax job, and I never WASH the car with running water, to keep the rusting process to a minimum ...I just WIPE with a damp chamois.
The only body repair job consist of a left front fender-bender many years ago. I've had three offers to buy the car at three different times.
So I'll keep on driving it and hope it lasts for the remainder of my life. I'm in the mid eighties, you know <g>
I just MIGHT do a oil-changing job using those ROTTELA oil . Walmart sells them.

Larry T

Eric
01-28-2008, 03:24 PM
Hi Larry,

Good stuff!

You could probably find a very serviceable used Corolla (or equivalent) for well under $10k; but it would be a much smaller car, of course.

I think it's ok to stick with what you've got. Though it's old, it is modern enough to be perfectly competent in service as a daily driver... and the drivetrain is both rugged and simple. Basic maintenance may be needed more often, but is easy to perform and does not require much in the way of costly parts (unlike anything new). And while it may not have air bags and so on, its size confers an inherent advantage, safety-wise, that probably makes it at least equivalent to something like a late-model Corolla.

Plus, it's a cool old car - and that's almost worth it all by itself!

ChevyMan
01-28-2008, 06:18 PM
Eric,
Corolla? Never!! I've been driving Chevys (remember my nickname..ChevyMan ?) all my life and will continue doing so.
Will changing to Rottela oil entail any flushing away of conventional oil, or do I just drain completely, then refill?

Larry T

Eric
01-28-2008, 07:20 PM
Eric,
Corolla? Never!! I've been driving Chevys (remember my nickname..ChevyMan ?) all my life and will continue doing so.
Will changing to Rottela oil entail any flushing away of conventional oil, or do I just drain completely, then refill?

Larry T


I'm virtually certain that Rotella not only meets but exceeds the service requirements Chevy lists for your car. But to be 100 percent sure, check the owner's manual and compare it with the API service rating of the Rotella.

ChevyMan
01-28-2008, 09:20 PM
Eric,
I have no owner's manual. Someone broke into my car about 10 yrs ago. I guess I can compare the API for Rottela and the Pennzoil I've been using so far.

ChevyMan
01-31-2008, 10:32 PM
This morning I added 53/4 gallons of 89 octane to my car containing a mixture of some older 89 and 87 octane. Why? I discovered that I could now easily start the car by just depressing the gas pedal once, and it would start without stalling, whereas prior to putting in 89 octane by mistake, I had to depress once, start, stall, depress once more, turn the key and it starts without stalling! So by the next gas stop I should have nothing but 89 oct in the tank.

ChevyMan
02-02-2008, 08:12 PM
Eric,
Corolla? Never!! I've been driving Chevys (remember my nickname..ChevyMan ?) all my life and will continue doing so.
Will changing to Rottela oil entail any flushing away of conventional oil, or do I just drain completely, then refill?

Larry T


I'm virtually certain that Rotella not only meets but exceeds the service requirements Chevy lists for your car. But to be 100 percent sure, check the owner's manual and compare it with the API service rating of the Rotella.





I think I'll stick with Pennzoil 10W30 which I've trusted for a long time. Somehow, I don't know if Rotella T will make too much of a difference and I don't know how long I can keep the car. Rotella T's API'sas I see are CI-4 plus,CH-4,CG-4 , to name a few, and Pennzoil are in the API SL, SM etc.

Eric
02-03-2008, 09:13 AM
Eric,
Corolla? Never!! I've been driving Chevys (remember my nickname..ChevyMan ?) all my life and will continue doing so.
Will changing to Rottela oil entail any flushing away of conventional oil, or do I just drain completely, then refill?

Larry T


I'm virtually certain that Rotella not only meets but exceeds the service requirements Chevy lists for your car. But to be 100 percent sure, check the owner's manual and compare it with the API service rating of the Rotella.





I think I'll stick with Pennzoil 10W30 which I've trusted for a long time. Somehow, I don't know if Rotella T will make too much of a difference and I don't know how long I can keep the car. Rotella T's API'sas I see are CI-4 plus,CH-4,CG-4 , to name a few, and Pennzoil are in the API SL, SM etc.


You might want to go ahead and use the Rotella.. for one Big Reason. It has the Zinc/friction modifiers that older engines such as yours need but which have been reduced or removed entirely from most oils.

chiph
02-03-2008, 11:44 AM
My high-school car was one of these.
Only in the GM green.

http://home.nc.rr.com/chiph/images/1973ChevroletImpala.jpg

robmcg
02-03-2008, 07:16 PM
The oil requirements for that Impala are API SF or better , and in temperate climates anything from 10W30 to 20W50 will work fine, your choice, seems like the car doesn't do hard work, but the older engines were built with wider tolerances than today.

Engine flushes are a waste unless you have black sooty sludge oli in the already and even then it's a line-call... two changes after reasonably runs are argusbly as good and would be my preference.

Fuel octane is an issue only if you can hear 'knock' or the engine is running poorly. I run cars with octane a few numbers above the minimum requirement; I get full-throttle 'peace of mind' and usually the higher octane has more engine-cleaning package.

just my 2c

Rob

ChevyMan
02-03-2008, 10:38 PM
Chip, what year is it?

Eric, I'll think about using Rotella T.

robmcg
02-04-2008, 01:51 AM
What is so great about Rotella T , Eric?

Major brand 15W40 SJ semi-syn is about as good as it gets for general purpose -10C-+35C and in most cars anything else is a waste of money.

All oil is somewhat 'cracked' these days and full of additives.
Additives don't lubricate, they stop foaming, they are detergent, they are long-polymer chains which when hot bind oil into strong thin film, and are disperants and antii-oxidants.

ALL the major brands are OK for newish cars, I would thing a 32-yr Impala in normal running with above freezing temps would be best with a fairly good ordinary oil of any brand but myself I would err on the side of heavier weight 'ordinary' stuff, but not 10W60 syn which is crammed with additives and too heavy for the mild driving you do. I use 15W40 SJ in my LS1 chev.

Also I repeat that engine cleaning with chemicals either fuel or oil is IMHO silly. Engines are designed to LIKE a bit of carbon. It spreads the thermal effects of flame fronts and improves cylinder sealing on older engines. One of the best things for an under-used urban engine is a long run. Both fuel and oil these days have additives which will clean an engine better than some very powerful additives. Like 'motor up' and similar these are complete frauds in my opinion.

My friend Margaret bought a 1995 Nissan 1.8 sedan in 1998 and it looked to me like it had never had an oil change in its life.. and as 'adviser' to her, I said, when she avowed that she liked it, that it DEFINITELY needed an oil change but may be OK... mechanic friends had extreme examples of these cars where the oil was so badly carbonated that it wouldn't drain! And there are a lot of cars out there which never get serviced until they break. That car now has nearly 200,000kms mostly traffiic and still runs well no smoke no noise..

so you see why I am no great fan of expensive oil for everday cars, "wasted money" in the opinion of my V8 mechanic guru friend Dave Walsh who builds race engines, stock car engines, and knows 10x what I know and his engines don't break.

chiph
02-04-2008, 01:44 PM
Chip, what year is it?

Eric, I'll think about using Rotella T.


It was a 1973. Got my first license in 1979.

350 small block, still took leaded gas (drank it like a fish, actually).

Chip H.

Eric
02-04-2008, 03:40 PM
"What is so great about Rotella T , Eric?"

It is one of the few oils that has not had the additives (ZDDP; zinc, manganese, etc.) reduced or removed. For older cars with flat tappet cams, there is a concern about valvetrain failures due to the absence of these friction modifiers...

robmcg
02-04-2008, 04:14 PM
"What is so great about Rotella T , Eric?"

It is one of the few oils that has not had the additives (ZDDP; zinc, manganese, etc.) reduced or removed. For older cars with flat tappet cams, there is a concern about valvetrain failures due to the absence of these friction modifiers...



Ah, when I last looked at some tests c1998 about half the common-brand oils had a little zinc... I thought they were only a last-resort thing when oil was failing in ordinary lubrication.

Eric
02-05-2008, 07:01 AM
"What is so great about Rotella T , Eric?"

It is one of the few oils that has not had the additives (ZDDP; zinc, manganese, etc.) reduced or removed. For older cars with flat tappet cams, there is a concern about valvetrain failures due to the absence of these friction modifiers...



Ah, when I last looked at some tests c1998 about half the common-brand oils had a little zinc... I thought they were only a last-resort thing when oil was failing in ordinary lubrication.


There is a great deal of debate in the old car hobby about this... the lay of the land is basically as follows:

ZDDP/zinc/manganese has been reduced or altogether eliminated from most 4-stroke gas engine oils; the automakers pressured the oil companies to take this step because of worries over premature failure (or reduced effectiveness) of catalytic converters. However, older engines with flat tappet cams (long out of production; probably the last OE use was late 1980s) require (supposedly) fairly high concentrations of ZDDP/zinc/managnese as a friction modifier. Operation without the additive is claimed to significantly increase the risk of premature valvetrain failure.

The argument strikes me as common sensical; engines of the '60s and '70s were designed given the oil available at the time; today's "emissions critical" oils may not have the additives, etc. they need - very much in the way that today's unleaded fuels can cause problems for an older high-perf. engine designed to run on leaded premium.

In any case, better safe than sorry, sez me. I add a bottle of additive (about $10) with every oil change. Since I change oil twice yearly, that's an extra $20. It does no harm - and it's much cheaper than an engine rebuild!

ChevyMan
02-05-2008, 03:16 PM
I've got some MM Oil left over and maybe I can use it to top off the level on the dipstick?

robmcg
02-06-2008, 07:57 AM
ZDDP/zinc/manganese has been reduced or altogether eliminated from most 4-stroke gas engine oils; the automakers pressured the oil companies to take this step because of worries over premature failure (or reduced effectiveness) of catalytic converters. However, older engines with flat tappet cams (long out of production; probably the last OE use was late 1980s) require (supposedly) fairly high concentrations of ZDDP/zinc/managnese as a friction modifier. Operation without the additive is claimed to significantly increase the risk of premature valvetrain failure.
....
In any case, better safe than sorry, sez me. I add a bottle of additive (about $10) with every oil change. Since I change oil twice yearly, that's an extra $20. It does no harm - and it's much cheaper than an engine rebuild!


Hmmm. I've never been a fan of additives, and rather thought that modern OHC and DOHC engines commonly had flat tappet effects in that the cam 'wiped' the cam-follower just as an OHV engine with mechanical flat tappets does.

I stand to be corrected, as ever.
Not sure if oil companies or independent testers publish a great deal about oil recipes and performance these days, either. It was near impossible to get the real oil (sorry, <g>) but viscosity/temp graphs I recall seeing from long threads in CServe CARS 'Oil' section showed considerable variation between various common brands and nominal weights especially at less than 200F temps.
I think 30-weight is on the light side for most engines in warm climate or high-temp; my V8-guru friend uses 15W40 SJ for everything including mechanical-tappet V8s which admittedly are more likely to crash in racing than wear with tappet-scuffing or blow up..

In his words, synthetics are "money down the drain". But he doesn't baulk at using them is a customer insists.

Back in the early 1970s I used a graphite molybdenum thing called 'Molyslip' in my 750 Triumph Trident with no apparent ill-effects after it was broken-in at about 2,000 miles of work and that was a very fast bike. Not sure if that was because of the additive or just luck...

I remain unconvinced.

DonTom
02-06-2008, 08:12 AM
"In his words, synthetics are "money down the drain". "

That's the way I've always felt too. At least for those who drive somewhat near normal. I don't convince very easily either. Not since I discovered that this world runs on BS.

-Don-

robmcg
02-06-2008, 10:57 PM
"In his words, synthetics are "money down the drain". "

That's the way I've always felt too. At least for those who drive somewhat near normal. I don't convince very easily either. Not since I discovered that this world runs on BS.

-Don-


But Marvel Motor oil additive is proven to make your engine run better. We have proof from independent customers.

Eric
02-07-2008, 06:56 AM
"But Marvel Motor oil additive is proven to make your engine run better. We have proof from independent customers."

Not the same thing.

ZDDP is what used to be in virtually all motor oils - just as lead was once in all gasoline.

The engines designed to use that sort of oil - just as the engines designed to burn leaded fuel - require those things to operate properly.

robmcg
02-07-2008, 08:15 PM
ZDDP is what used to be in virtually all motor oils - just as lead was once in all gasoline.

The engines designed to use that sort of oil - just as the engines designed to burn leaded fuel - require those things to operate properly.



So it's your opinion that modern US oils don't have very good scuffing properties?
I don't think I have ever seen an engine which has suffered damage because of poor SG-SJ oil of common brand. But I can see that is an oil has a package with ZDDP it might be nice with an older engine, but it's like running engines with soft valve-seats with unleaded? I don't think it's that extreme, and have no proof.

Eric
02-12-2008, 08:23 AM
ZDDP is what used to be in virtually all motor oils - just as lead was once in all gasoline.

The engines designed to use that sort of oil - just as the engines designed to burn leaded fuel - require those things to operate properly.



So it's your opinion that modern US oils don't have very good scuffing properties?
I don't think I have ever seen an engine which has suffered damage because of poor SG-SJ oil of common brand. But I can see that is an oil has a package with ZDDP it might be nice with an older engine, but it's like running engines with soft valve-seats with unleaded? I don't think it's that extreme, and have no proof.


I'm not an engineer, so I can't say with authority. However, I accept the warnings that have been issued by engineers/engine builders, for example, the folks at Competition Cams.

I'd rather be safe than sorry - especially with an antique car that has a long out-of-production engine. Why risk engine failure over a $15 additive? If it's not really necessary, I've lost $30 (two oil changes annually). No harm done. But if I don't use the additive and a cam lobe(s) fails, potentially catastrophic damage will have been done...