RLSH700

Okay, I have had it up to my eyeballs with this ridiculous myth that the press constantly wants to inject everytime I turn around on how to cut corners. They constantly do these ignorant stories that imply that any fuel besides regular is unnecessary. They will make claims that because it is only recommended, it is therefore unnecessary. The flaw in their logic is that this depends a lot on engine electronics being able to 100% of the time cover for this. The problem I have with this myth is I have seen numerous situations where engines on more recent cars where mid-grade and premium were merely recommended, had the engines detonate. Although I'm sure if the proper grade of fuel isn't available regular will do, constantly filling it with the lower grade fuel is taking a risk. I have found that despite the recommended claim that engines that recommended more than regular would knock and ping if it did not have the proper grade. Your thoughts?

MaybeChallenger

I had a customer that had to make three trips to Texas from here in So. Ca. in his Lexus ES330, '04 I believe. He said he was going to try one trip with premium and one with regular because we had chatted about the claims of performance. I had been told for many years that premium gives better mpg. Well his "test" showed that the trip with premium gave him 2mpg and I did some calculating and that made premium use about 2 cents a miles cheaper than regular and better throttle responce and acceleration. And thats just my 'two cents"

RLSH700

I've also noticed in some vehicles (including some that only are rated for regular) that for some reason, if you use mid-grade it doesn't gear hunt as often (normally over short hills where it would jump out of OD right as it reached the top of the hill when running 89 it wouldn't be as quick to downshift).

jdb840

I think it depends on the car and compression ratio. I am you RLSH700, I would be worried about pre detonation. Mostly on cars with forced induction, is when I would have say it would get worse mpg and possibly blowing up the engine.

When I had my grand prix gtp, it would knock so bad if I used 87, sometimes I would see up to 7 degrees of KR (knock retard). Which eventually caused the car to run supper lean and blew a chunk off of my piston.

I don't think if a vehicled call for regular and you put in high grade it would make a difference on mpg.

RLSH700

From what I have observed and especially in the case for forced air induction, what you say is true. My friend had a 98 GP GTP and only once did he put regular in it. After that, he stuck with premium and the highest octane premium he could find. I think that in a case for using higher than regular grade in a regular grade requiring car, where you have flat roads with no hills and the risk of downshifting does not exist, there is probably little to no difference, but in the situation that I observed, I believe a difference would arise.

lear4406

The cars today have a computor and knock sensors. They will detect knock and cut timing. So if you want the HP you have bought the car for, I would go with the advertised octane. If you use lower rated fuel you will lower the HP rating. I always go with 93 oct. and want the best HP I can get at all times. I even add 109 octane when going to the track so I get the best performance out of the engine I can get and to add insurance to keep the engine safe from detination. I would only use lower octane in the case of an emegency and I would also baby the car while the cheap stuff is in there.

73sixpack

The newer (computer controlled) engines are very good at controlling detonation with timing retard. I don't think I've ever noticed it on a fuel injected car, or on the old "lean burn" cars. A different story on the 6 pack motor, (10.5 CR) with the headers open you can't hear it going on but I'm sure it was rattling like a hammer on an anvil once when we mixed 1/2 & 1/2 pump gas and racing 110, it blew the center out of a spark plug on a 1/4 mile pass. Around here it's hard to find anything but 87 octane without alcohol in it.

RUBBERBNDMAN

At $4 bucks a tank more I'll keep using the 92.

MoparJoe

I have been using 87 Octane in my Jeep Grand Cherokee 5.7 Hemi for 2 years now. No problems, but it does not have the balls that my Challenger had. My wife's 06 Charger 5.7 hemi also uses 87 Octane. Ypou really think this could affect the longevity of the engine ?