gas mileage

[mikewb]

I have heard that if you run 91 octane  although more expensive you can get better mileage. true?

[Captkaos]

False.  All it does is deplete your wallet of extra money.
In factory for all these motors should run off of 87 octane. 

[76 k10]

i think so cuz if i run 87 my truck sucks that stuff down like you wouldnt belive! but i like to just run 89 its a lil cheaper and it last 10 times longer try that

[VileZambonie]

higher octane is less combustible at lower temperatures. The only real benefit is resistance to knock in higher compression ratio applications.

[TexasRed]

so yeah, it might give you a little more mileage because your timing may be a little too advanced, or for some reason your compression is higher and you get knock so your ESC kicks back the timing.  But everything stock, 87 is the way to go. Unless, you can get less ethanol by going to 89 or higher.

[76 k10]

i have a stock bottom end i think? all i have is a chevy 305 with a good size cam. and headers and a qjet carb and a stock intake

[Unofficial]

So will running a higher octane allow the engine to run cleaner? Once I swap over to my bored out 350, I want to run the best gas, but not if it doesn't even make a difference performance/cleanliness.

I guess I'll just have to run race gas

[eventhorizon66]

Cleanliness has nothing to do with octane.  Select the octane that works with your compression ratio and timing.  If stock, 87 is just dandy.  Heck, I'd put 85 in mine if it were available.

[VileZambonie]

No, it will just allow you to have higher compression ratio's without self ignition/ preignition issues. If the air fuel charge ignites before the spark plug fires the results can be catastrophic. If you want I'll take a picture of a piston that suffered from detonation that I have. Detonation occurs when the air fuel mixture explodes resulting in colliding flame fronts within the combustion chamber. The result is a sonic boom that resonates through the engine sounding like a "ping" Although you hear ping, the engine suffers like two hammers being smacked together. So unless you NEED higher octane fuel to take advantage of optimum spark advance without this happening you are wasting your $$$$$

[TexasRed]

I think back in the 60's they added stuff to premium gas to help keep the injectors clean in corvettes who required premium. I'm not sure but I think some of the VW air cooled beetles were fuel injected too.

[VileZambonie]

If you want to clean your fuel system there are some pretty aggressive cleaners out there, but don't rely on the gas to do it for you. Fuel company's are misleading with their advertisements and labeling higher octance as premium. the price is premium that's about all.

[eventhorizon66]

On the topic of cleaners.  What do you guys recommend?  I just use Techron concentrate.  I've tried Redline's cleaner as well, but it's difficult to find in my area and I don't really think it's worth hunting down.  I hear alot about people using Seafoam too.  Mainly about people dumping it in their vacuum lines until the engine dies and adding to the crankcase as well.  Can you say spun bearings?  LOL, knuckleheads.

[Lt.Del]

The only time i use 93 octane is when I am pulling my 7k lb camper trailer.  It does run smoother with a touch more power it seems when I pull my camper. Whatcha think?  is it my imagination?

[VileZambonie]

It won't run smoother, but will resist preignition especially with the increased engine temps.  So if your engine is lugging or pinging when you're loading it you might need a higher octane fuel especially when towing.

Sea foam or top engine cleaner works good for decarbonizing. I wouldn't add it to the crankcase though. Actually after you use it make sure you change the oil and filter. I wouldn't waste my money on any fuel system cleaner unless you have an MPI, or CPI system. The CPI's are the worst at getting clogged up but 3M makes a decent cleaner and so does BG.

[eventhorizon66]

Vile: I only use the Techron on my sister's Toyota and my mom's Acura (at the same time I change the oil on each one).  My truck just gets its fuel filter (stainless disc reuseable type) cleaned out periodically.  What procedure would use recommend for top engine cleaning with Seafoam?  Pour in the main PCV vacuum hose or directly down the carb?  Pour until it dies!?! or just until it bogs down a bit?  Then change the oil after it stops blowing that white smoke.  Does seafoam get along with catalytic converters ok?  Do you use it on any of your rigs?