What octane are you running?

The octane rating of gasoline gives an indication of the fuels ability to resist detonation. Generally, with gasoline engines, the fuel is already present with the air and so can ignite from the heat generated through compression. For this reason high compression ratio engines often specify high octane fuel. When towing, the throttle plate is often wide open allowing unrestricted flow of the air/fuel mixture to more efficiently fill the cylinders. At low rpm this can cause the fuel to ignite prematurely, especially in engines with higher compression ratios. Often, burning high octane gasoline in an engine designed for low octane gasoline can result in poor fuel economy. Likewise, burning low octane fuel in an engine designed for high octane fuel can yield poor fuel economy. Because I am at higher altitude and seldom drive our Acura with the throttle plate wide open I get away just fine with low octane fuel even though the manufacturer recommends high octane gasoline only.

The Cetane number used to rate diesel fuel describes the fuels ability to ignite (as opposed to its ability to resist ignition in the case of octane rating). Higher cetane fuels will ignite more readily and tend to run more efficiently but there is a trade off, higher cetane fuels usually have a lower energy density. European diesel and 100% bio diesel have higher cetane values than American dino diesel.

jalichty wrote:
Run 87 in my Camry Hybrid, but don't tow with it. Don't know if the diesel I use has an octane rating and it doesn't seem to know the difference between towing and not, no pings. LOL

Diesel fuel has a cetane rating. And they can ping amidst all the clatter.

Run 87 in my Camry Hybrid, but don't tow with it. Don't know if the diesel I use has an octane rating and it doesn't seem to know the difference between towing and not, no pings. LOL

I usually run 89 when towing, 87 & 89 alternating when not.. :)

Right at 15 for my Duramax. :B

I had an '06 1500 RAM Hemi. I ALWAYS ran 89 octane when towing. The computer will attempt to delay the timing with 87 octane to eliminate spark knock. That results in a lack of power when you need it the most.

I fill up with the best priced gas I can get and always in the 87 octane range.

6.2 F 250 towing 11.5K fifth wheel, to include back and forth thru the smokies.

My Acura states premium only. I use regular which yields me exactly the same fuel economy as the premium does. I can see why towing might require a higher octane.

I ran 89 octane in my '05 Hemi powered 2500HD the whole 120k miles I owned it. That was a strong engine for it's size.

FWIW - i run 87 octane, but I had to turn up the fuel mix at WOT to avoid pinging because the AFE intake flows so much more air than stock it was leaning out.