OK - - what gives with the different gas types??? My last few cars (all honda accords) stated right in the book to simply use regular unleaded. My current car (chrysler 300m) states to use, at minimum, the mid-grade.

I have been using the mid grade, but wonder really what the advantage of one over the other is and why use one vs the other?????

my car takes premium so i know what you are talking about,

basically, the difference between regular medium and premium, is their tendency to spontaneously ignite,
due to heat in the engine.

this heat comes from the air being compressed in the cylinder, the more compression, the more heat, the more likely the gas is to detonate.

the higher grades of gas are basically saying, you can compress them more, and they will not ignite prematurely.

So the compression ratio of your chrystler must be higher than that of your hondas.

basically you can use any grade of gas in your car as long as it doesnt knock (ignite prematurely(before the spark plug ignites it))
but chrystler is basically telling you that that point is any grade under medium.

I never used to think octane made a difference, but in 1999 I bought my first new car in 20 years and wanted to be sure to treat it right. I've never put anything but premium in it.

After over 65,000 miles, when my oil gets changed (religiously every 3,000-4,000 miles), my oil comes out as clean as it went in.

I thought that octane had something to do with how hot the gas burned in the engine, but I was looking at this site: www.ftc.gov/bcp/conline/pubs/autos/octane.htm
and it doesn't look like that's the case.

Regardless, my car is as good as the day I bought it, so I plan on continuing to treat it to premium fuel.

Good post!

In todays cars, most knock comes from low compression engines. A friend did deliver gasoline to service stations and he said at his company it all came from the same tank, just went into different holes. Studies have been undertaken on gasoline and all have shown that there is no need to burn anything beyond "regular" gasoline. I have had brand new cars that have had spark knock and the factory said that was normal............. Don't waste your money...........

Lydia: bibc14's explanation is essentially correct. Higher octane fuel resists detonation upon compression. Most new cars are designed to run their best on 87 octane. Higher octane does NOT give you more power and performance as the adverts tell you. High octane fuel in an engine that does not call for it will not burn as completely and in turn more unburned fuel is dumped out of the exhaust, and with it your hard earned money. I don't recall your Chrysler requiring high octane fuel, but my years were spent with General Motors so I certainly could be wrong. As I mentioned earlier most engines are designed for 87 octane, so I would try it in your car and I will bet that it runs just fine. Another respondent mentioned his engine oil coming out clean after 3-4 thousand miles. This would scare me to death. The purpose of the oil is not only to lubricate internal moving parts but also to collect dirt and impurities and carry them to be collected in the oil filter. Oil coming out exceptionally clean is an indication that it may not be doing its job properly. I have seen oil come out like this but only in vehicles with very elaborate porous bronze filtering systems. Anyway, getting off the track here. Try the 87 octane in your car. It will not hurt anything and if it runs fine then use it and save yourself a couple bucks.

I think the main reason why my engine is still so clean is because MOST of the miles I put on my car are HIGHWAY miles of 55+...So my engine is working at it's maximum capacity most of the time.

I'm not concerned that my oil comes out clean due to that, but I will continue to get it changed on schedule.

If I had city driving to contend with and this was happening, yes, I might be concerned!

When my last truck started to get up there in miles there was a noticeable difference in performance with Regular VS Supreme. It would run great on Supreme but it would idol rough and lack power when I'd fill it with regular.

Since 85% of my driving is stop and go city driving I tend to always by Supreme, even though my new truck runs great on regular, I just feel more comfortable filling it up with Supreme.

Old post but an interesting one as my wife bought a 2002 Honda Accord and the idea about regular gas got me wondering as well-Nice car but one thing bothers me-I may have to go bald as my head easily hits the sunroof-LOL-My thick hair easily grazes the roof