Here’s the latest reader question, along with my reply!
Oskar asks: I have a jeep Patriot with the 2.4 liter Tiger Shark 4 cylinder engine. These engines regularly run over 200,000 miles without a hitch. On the Patriot blog I frequent, they have a Pat with over half a million miles on it and with 7 owners. Pretty much bullet proof. My question: Running 89 octane fuel seems to make the engine run better. (smoother, more pep). Will this hurt the motor over the long haul since I plan on holding onto this jeep for many years?
My reply: There are two things to consider here, one easy and obvious – the other one more a trial and error thing.
The easy – and obvious – thing is octane.
Your Jeep’s engine was designed to run best (most power/performance, highest mileage) using gas with a specific octane rating, which refers to the fuel’s resistance to premature ignition from pressure and heat rather than spark. Engines with higher cylinder pressures (from higher compression or turbo-supercharging) generally – but not always – run best on higher-octane fuel. 
Conversely, engines designed for lower-octane fuel will not – generally – benefit from using high octane fuel and may even run not-as-well (not in terms of physical sensations; the idle quality and so on won’t change – but you may notice a reduction in power/mileage).
The thing that’s sometimes confusing is the conflation of high-octane with “premium” gas – and the implication that “regular” is low-quality (rather than lower octane) gas.
Both fuels maybe of equal quality – just different octane.
With a caveat.
Some “premium” fuels will have a different – and possibly, better – additive package. This varies according to the brand of gas. And the same is true of “regular” gas – sold by different gas stations. 
So, I have two suggestions:
First, grab your owner’s manual and look in the index under “fuel” or “fuel requirements” and see what Jeep recommends as regards octane for your Jeep’s 2.4 liter engine. According to my manuals, the 2.4 liter engine is a regular (87 octane) fuel engine. But double check your manual; there may also be a sticker on the inside of the fuel door.
Abide by this.
Now comes the trail and error part.
Try different brands of 87 octane regular and see whether you notice any difference. If you find that (as an example) your Jeep seems to like Exxon’s 87 regular better, go with that – and so on!
. . .
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The engines may be great, but our rural mail carrier’s Patriot has been in the shop for two or three months with electrical problems so she has been driving her four dour Ram since then.
From the frying pan, into the fire. I’ve run many company Ram trucks that had horrible electrical problems. A few of us were cruising along I 20 one morning and smelled smoke and then notice fire. We pulled over and snuffed it out. Whatever it was didn’t keep it from running so we just went on. After that everyone expected another one. Since I operated a big rig and other equipment, I didn’t ride in it often and don’t know if it had to be repaired under warranty but was just used in the hope it would burn to the ground.
That was a roustabout truck, a 5500, with a 3′ deep front bumper with chain vices on each side so you could make up pipe connections. A guy in a Ford 150 pulled right out in front of it one day. The 150 was mangled sheet metal and the 5500 was practically unhurt which pissed off everybody. The owners wanted it to blow all the air bags and be totaled(it was a rolling problem from the cooling fan to the unit that ran the speedo on the rear-end. Best thing about it was the Sirius radio and stereo.