Ideas Needed: Why sudden drop in mpg?
I always seem to average right around 8.5 mpg however the return leg of this last trip I saw averages around 7.5 and that concerned me. I'm looking for reasons this could have happened.
1) The return leg used 10% ethanol gas during 7.5 and no ethanol during 8.5 legs - could that be the difference?
2) I worried I had a stuck caliper (Workhorse brakes - but my VIN is exempt from the recall). However, after 70 mi, the rotors/calipers were near ambient air temperature. No mushy brakes and no "burning" smells either.
3) Headwind? There was wind from the drivers side, straight into the MH (not tail or head).
4) I tow a CRV - verified no wheels locked, no parking brake, everything looked perfectly normal there. No hot wheels.
5) I drive at a constant 63mph (towing max on the CRV is 65), that gives a pretty constant 2200 rpm (varies with hills of course). This was constant during times of low mpg.
6) It was very hot outside - but using engine A/C did not make any difference in mpg reading.
7) I did look at instantaneous mpg and on level road it varied a lot: low of 6.0 high of 10.2 and it was jumping around erratically. Made me wonder if the "mpg" computer was accurate. However, it seems as though I did use more gas on the return leg than normal so I suspect the lower mpg was real.
Could there be anything with the engine that I should check? It ran and sounded just fine. Lots of power as always. No funny noises.
The autopark brake was performing normally. I could coast down a slight hill with engine in neutral (ie, autopark brake was not dragging) and when the autopark was engaged, the MH would stop almost instantly.
I'm at a loss for any other ideas.... what should I check to explain the lower mpg?
1) The return leg used 10% ethanol gas during 7.5 and no ethanol during 8.5 legs - could that be the difference?
2) I worried I had a stuck caliper (Workhorse brakes - but my VIN is exempt from the recall). However, after 70 mi, the rotors/calipers were near ambient air temperature. No mushy brakes and no "burning" smells either.
3) Headwind? There was wind from the drivers side, straight into the MH (not tail or head).
4) I tow a CRV - verified no wheels locked, no parking brake, everything looked perfectly normal there. No hot wheels.
5) I drive at a constant 63mph (towing max on the CRV is 65), that gives a pretty constant 2200 rpm (varies with hills of course). This was constant during times of low mpg.
6) It was very hot outside - but using engine A/C did not make any difference in mpg reading.
7) I did look at instantaneous mpg and on level road it varied a lot: low of 6.0 high of 10.2 and it was jumping around erratically. Made me wonder if the "mpg" computer was accurate. However, it seems as though I did use more gas on the return leg than normal so I suspect the lower mpg was real.
Could there be anything with the engine that I should check? It ran and sounded just fine. Lots of power as always. No funny noises.
The autopark brake was performing normally. I could coast down a slight hill with engine in neutral (ie, autopark brake was not dragging) and when the autopark was engaged, the MH would stop almost instantly.
I'm at a loss for any other ideas.... what should I check to explain the lower mpg?
