worse MPG with 89 octane?
#1
worse MPG with 89 octane?
My truck is a 2003 5.7 4X4 quad cab currently with 75k miles. i have had it about 6 months and it had 67k miles at the time. For the first 4 1/2 months i ran it on 87 octane and was getting 12-13 mpg. After reading info on this site, I switched to 89 octane and have been running it for about 6 weeks and in that time i have run 6 0r 7 tank fulls of gas averaging 9.5 to 10.5 mpg. No other changes have been made. Once during this time i ran a tank of 87 (due to funds) and it seemed like the mpg increased a little. Now, my driving habits are not more aggressive with the 89 octane. I switched to avoid issues with engine damage, but with 74k on the truck already, i am guessing it may have been run on 87 most of its life? The truck runs great on either gas. i am a bit confused. is this normal? The truck does have an AEM intake and gibson exhaust if that matters.
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#8
The only way to get accurate mileage information is the tried and true pencil and paper method. Plus, you MUST fill the tank absolutely full -- pump cut-off is not accurate enough. My truck gets a smidge under 14 on my commutes and almost 18 on the highway (if I keep it at the limit). Who, me?
#10
some clarification, i get the mpg via pencil and paper. I only use the overhead to kind of moderate my driving habits, but I doubt its accurracy. I have been getting the gas (both octanes) at the same station. I didnt switch to increase mpg, I did it in fear of doing some sort of damage with the 87 octane. I am thining about the tuner idea, but i dont need more hp (I know i'm getting old). so i dont know. I just couldnt figure out the worse mpg, I figured it would be the same at least.