Proper/Optimal fuel grade for GMC

[mark sawyer]

FWIW, I try to fill the coach up with E-Zero and Stabil when it's going to sit for an extended period.... (Our big, flat tanks have a lot of surface
area for condensation to form) But on the road I fill with whatever "Top Tier Gas" gas station is convenient.

Jim Hupy: I am unfortunately too young to have experienced the 50s or bought 105 octane leaded fuel outside a racetrack (at like $10 a gallon)... But
don't poo poo the ethanol too much, as it also just happens to be around 105 octane if you have an E85 pump in your vicinity.

I bet even in the 50s, you couldn't get 105 octane fuel for 20 cents less per gallon than the cost of good old regular gas.... Even with the fact
that you need to burn more of it, it's still a screamin' deal if you are looking for cheap, high octane fuel...

And in a boosted engine, the ethanol will pull a good deal of heat out of your intake air temps as it vaporizes... (Like a chemical intercooler) With
the intake air temp drops, the E85 performs like it has even higher than 105 octane....
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX

 

[mghamms]

I'm not going to get into a big discussion over the pros an cons.
I never use mid grade 89 its only a dime less than premium 93 here.
So I usually fill with regular and add premium win I feel I need a little more octane.
Average about 1/3 maybe 1/4 premium blend. I never did the math but I do have the records.
--
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts

 

[jim kanomata1]

If nothing else, the Premium has Lot more additives to clean carb and
internals as well,

On Mon, Aug 24, 2020 at 2:06 PM Mike Hamm via Gmclist <

> I'm not going to get into a big discussion over the pros an cons.
> I never use mid grade 89 its only a dime less than premium 93 here.
> So I usually fill with regular and add premium win I feel I need a little
> more octane.
> Average about 1/3 maybe 1/4 premium blend. I never did the math but I do
> have the records.
> --
> 1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
>
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502

 

[lw8000]

Just my experiences, but the high ethanol content of today's fuel has caused us a ton of headaches. Not only has it eaten away at various components
of the OEM fuel system, but it causes vapor lock which is very frustrating. Using ethanol-free fuel would completely resolve these worries, but like
some have said, finding that is not as easy in some areas, so a lot of us just have to use the crap-a-hol common 87 octane. There are a lot of
workarounds to help with vapor lock but it does involve some time, money, and patience to resolve it (as has been discussed here in this forum). I'm
always happy to share my experiences and how we resolved with the OEM fuel system (side topic).

It is extremely important to add Sta-bil to the tank when letting it sit for a while (several months or more). I have found Sta-bil to prolong the
life of new fuels for years (in other vehicles).
--
Chris S. -
77 Kingsley, 3.70 FD, mostly OEM -
S.E. Michigan