I figured out my gas mileage issue

[dumbucket1]

My blazer has only been getting 9 mpg in city driving. My 76 silverado also gets 9mg in city driving both have 350's in them. Well i didnt realize it but I have been buying a 89 octain fuel with 10% ethanol mix. I switched to 87 octane straight gasoline and my mileage has jumped up to 13 mpg city driving in the blazer. Havent tried it in the truck yet but I am sure it will be the same. I am guessing if I went with a highter octane straight gas blend gas mileage would go up even more. So just a thought if others are having issues with their gas mileage.

[VileZambonie]

What made you go to 89 octane? 87 is more combustible than 89 at lower temperatures... The only reason to use a higher octane fule is if your compression ratio warrants it.

[dumbucket1]

89 octane was cheaper than 87

[VileZambonie]

Say what? 

[VileZambonie]

Ahh you're out in Il... that's why

[Dragon]

My blazer has only been getting 9 mpg in city driving. My 76 silverado also gets 9mg in city driving both have 350's in them. Well i didnt realize it but I have been buying a 89 octain fuel with 10% ethanol mix. I switched to 87 octane straight gasoline and my mileage has jumped up to 13 mpg city driving in the blazer. Havent tried it in the truck yet but I am sure it will be the same. I am guessing if I went with a highter octane straight gas blend gas mileage would go up even more. So just a thought if others are having issues with their gas mileage.

Arco/BP/Citgo user I take it???  The ones in my State have been Notorious for doing Ethanol Blends without marking the pumps for years!! To the point they were screwing up Cars/Trucks/Etc, and they recieved fines along with Property Damage Lawsuits   I find it funny that it is all the rage again for them to do the blending, but no one wants to remember the past, nor understand why they get crummy MPG's with it!!!   Sure a blend might be slightly easier on the Enviroment(so they tell you), but if you get crummy MPG's with it, doesn't that mean that you have to use more to make up for it

Try staying away from any station that offers a blend, cause they are doing it to all their Gas...  As for using a Higher Rating, I wouldn't go higher than the next one up from 87 Non-Blended... Unless as Vile stated, your Engine warrants it...   

My Daily is a '96 Chev Caprice with a 4.3(265 V8) that has been Performanced Tuned and Modded to run 92..  Sure it can be a pain in the wallet to run it, but it is nice to have a Boat that gets 17/20City & 26/32Hwy(Dang foot causes variations ).... Having Cruise would help(Hope to add soon, before I adjust back to a fuel saver tune) it be more steady, but it is fun to bury my foot at times(The Nice Burble for my Custom Tubulars don't help either)

[dumbucket1]

yep citgo/caseys general store is where I usually buy gas cause they are close to my house. There is a shell nearby also but its on the wrong side of the street to get back on the road without waiting forever for traffic to clear up.

[Fordeatinz71]

what's that baby LT1 run in the 1/4 Dragon?  got any pics?

[Dragon]

yep citgo/caseys general store is where I usually buy gas cause they are close to my house. There is a shell nearby also but its on the wrong side of the street to get back on the road without waiting forever for traffic to clear up.

Watch the Shell Stations even, there are some here that have been doing the Un-Marked blending as well(Maybe just a Private Owner thing, but still)!!   I filled up one of my tanks with it as a Reserve, shortly after switching over to that tank, I noticed a bit of coughing & Sputtering, which disappeared after filling up at another Station.... So far Chevron/Texaco/76 are the ones I have no trouble with, and are worth the extra cost through mileage..

what's that baby LT1 run in the 1/4 Dragon?  got any pics?

PM Sent

[77c15]

I may be completely wrong in throwing this in the mix, but when I removed the glovebox out of 74 cab I stripped out, I found a sticker that says the truck requires a 91 octane minimum to keep from knocking!

[VileZambonie]

You are not wrong. In 74 higher compression ratio's were still used. In fact many of the Big Blocks were factory domed pistons.

[gezn2]

I may be completely wrong in throwing this in the mix, but when I removed the glovebox out of 74 cab I stripped out, I found a sticker that says the truck requires a 91 octane minimum to keep from knocking!

 
That's probably a 'Research' octane number, the octane posted on gas pumps is 'PON' which is the average of the 'Research' and the 'Motor' octane tests, IIRC those yellow stickers didn't show up until about 1980 or so.........
A long-winded explanation can be found at http://en.wikipedia.org/wiki/Octane_rating 

[77c15]

That link was helpful, but my head started to hurt...I should have paid more attention in chemistry!