Thread: Premium gasoline vs. the other stuff

Tweet

I'm starting to drive my car a bit now and the gas tank is headed towards fumes - it gets surprisingly good mileage - and it will need replenishment soon. The price difference of premium vs the 87 "regular" almost makes me sick -$.30 to $.60 a gallon more. What am I really giving up between the 87 and 91 octane? The engine is not particularly hipo with 9.0 compression ratio, a Ford 'E' camshaft with 1.7 rockers and an Edelbrock 1405 then fired off with a full MSD ignition system. My guess is - not much as long as I drop the initial timing a degree or two, 10 to 8.

Comments from the others here??

(and yes, I AM cheap {think broke}with a new $$$$$ roof being installed on my home as I type this)

It should be fine at 9.0:1 .. I run premium in the Beetle, because it gets better gas mpg on it, but it's a whole diffrent ballgame being air cooled... you may be able to go mid grade without any tuning, but getting 'fresh' premium/ midgrade can be an issue also. I got a couple tanks of stale premium before. Beetle doesn't like it.. That might be an added benefit to converting to 87

Try a quickie test....put a few gallons of the cheap stuff in the tank and drive the car....fast, slow, hot, cold, highway, city, etc and see how it does. If it pukes, fill the rest of the tank with the good stuff, if it runs OK, you know that you can whiz in the tank and it will run.

mike in tucson

JMHO, but a 9.XXX compression engine should work fine with 87 octane. It is the other stuff that they add that will help or hurt the performance. I had a 74 Camaro that I drove as a daily driver around 2002 to 2006. It ran fine with the Chevron with Techron with 87 Octane. But if I went to any other fuel, it would ping if it wasn't the 91 octane.

That was kinda my idea. Unfortunately here in my part of the world we have Hess and what everyone sells which comes from the same bulk supply plant, regardless of the price - and I'm no longer sure about the Hess If ol' Leon Hess was still with us - I can assure you that they wouldn't sell any one elses gas - he was tough to deal with!!!

Dave,
I like Robot's approach, try a few gallons of the 87 octane and see if it pings at full throttle through your load range, and especially at your cruise rpm when you'll be pushing it on grades, passing, etc. If you get minor pinging then try backing off the timing a couple of notches as you said. Increased octane slows the burn rate in the cylinder, so you actually get the highest efficiency running the lowest octane that your engine can stand. The old adage that premium gave more power was simply not true on a given engine and no change in timing.

Originally Posted by rspears

Dave,
I like Robot's approach, try a few gallons of the 87 octane and see if it pings at full throttle through your load range, and especially at your cruise rpm when you'll be pushing it on grades, passing, etc. If you get minor pinging then try backing off the timing a couple of notches as you said. Increased octane slows the burn rate in the cylinder, so you actually get the highest efficiency running the lowest octane that your engine can stand. The old adage that premium gave more power was simply not true on a given engine and no change in timing.

Roger - great idea - except I have about as much chance of hearing a ping as you do with yours The engine exhaust "music" is kinda overwhelming to my 50% hearing loss ears along with that wind rustling all 157 hairs still on my head. I'll knock the timing back a degree or two.

Yeah, I do know about the slower burn/combustion rate. I think the last car that needed 'premium' was my '86 Mustang GT - 87 made that one sound like a death rattle.

Originally Posted by Rickomatic

JMHO, but a 9.XXX compression engine should work fine with 87 octane. It is the other stuff that they add that will help or hurt the performance. I had a 74 Camaro that I drove as a daily driver around 2002 to 2006. It ran fine with the Chevron with Techron with 87 Octane. But if I went to any other fuel, it would ping if it wasn't the 91 octane.

I've had the same experience with Chevron. My Ex wife had a Buick that would only run on premium from Chevron. It would ping like mad on every other brand. I drove it one day and it was pinging and I asked her if she stopped at Chevron. She said no, she didn't feel like driving that far so she got hi test at some other station. As soon as we put Chevron back in it the pinging went away.

Don

Good luck on the 87 octane! I was just reading about the Chevy volt it also requires premium, although only a 9.7 gallon tank. Green car Hmmm.. My neighbor just bought an almost new Mitsubishi SUV also requiring premium, big tank on that one, he hates it! It's a conspiracy I tell ya! I'll just stick with my 350 tune port, not much power, but that one you probably could run on whiz!

Yeah, I thought about the exhaust noise, but did not know how loud yours is - concept is good, anyway... Maybe you can enlist a young neighbor kid that hasn't blown his ears out yet with ear buds & Ipod to listen for you??

Originally Posted by rspears

Yeah, I thought about the exhaust noise, but did not know how loud yours is - concept is good, anyway... Maybe you can enlist a young neighbor kid that hasn't blown his ears out yet with ear buds & Ipod to listen for you??

Flowmasters are never very quiet - even the 3 chamber version

Neighbor kid with any hearing left