For the last two months there’s been a significant drop in my 2012 v’s gas mileage that I can’t explain. Since the weather warmed up at the end of June and for several thousand miles I’ve been averaging 46-48 mpg per tank in highway driving over the same route. I use eco mode and try to drive at speeds between 60-65 mph, modulating the peddle pressure to keep the HSI from exceeding two bars past the center mark. At my recent dealer service (done in August at 13K miles) I had the dealer turn off the reverse beep. Other than that only routine inspection and servicing was done. Immediately after the dealer service my mileage started dropping and for the last five tankfuls it has been on a downward slope. My last tank over the same highway route averaged 42 mpg. The obvious explanations for a drop in gas mileage don’t seem to apply. Ambient temperatures haven’t changed significantly. Tire pressures are checked often and kept at 2 psi above recommended values (37 front, 35 rear). There is no sign of a wheel alignment problem. The only thing I can think of is that something was inadvertently changed in the engine control module when the reverse beep was shut off. Is that possible? Or can other changes be made to the hybrid system that could account for the drop in mileage?
I check tire pressures every two weeks and always after a dealer service. 37/35 is what I've been using since new.
Nevertheless, 5lb over recommended is the best for MPG. I'm guessing your drop in MPG has no relation to the service visit. The OE tires are not known for good MPG, so you're not doing too bad. Better than I ever did on them.
Check your oil level? There's been cases before where the oil was over-full, causing the mileage to drop.
"Routine inspection" likely included brake inspection. Maybe they tightened the parking brake cable excessively? If you can raise the back end, parking brake released see if the wheel turns reasonably freely. Is it rear discs? If so there'll be constant slight amount of drag, but not that much.
Parking brake seems properly adjusted. When each rear wheel is raised it can be turned easily with one hand when the brake is released, spinning several revolutions although not free-wheeling. When stepped on firmly the brake engages fully at seven clicks. So I'm back where I started, looking for reasons why my mileage has dropped. Again, maybe someone who understands how the ECU works could tell me if an accidental change in some ECU parameter, made while changing the reverse beep to a single beep could affect the hybrid tuning in some way. Thanks to those who posted and tried to help.
Is there anything about the way it drives or ride that has changed? Do you notice the ICE running when before it was not in a similar situation? I had my reverse beep turned off shortly after purchase but noticed no changed in mileage.
No noticeable changes in the way it drives, in acceleration . But the instantaneous mpg readout tends to be lower than it used to be for a given driving condition -e.g when driving at 60-63 mph on a level stretch of road. Also at low speed the ICE seems to run more than it used to but I'm not sure. It seems to want to charge the battery more often, keeping the charge level at 7 bars (used to be 6 bars). I could be wrong on this though...
Right. But what if the tech accidently changed some other setting in the ECU while attempting to turn off the reverse beep. Is there anything that could be altered in the ECU that might affect gas mileage?
Reality check: Your MPG is actually quite good compared to "average". Your perceived drop in MPG is actually pretty small, too small to be looking for some mysterious issue. Your Fuelly averages look to be pretty normal, and follow expected seasonal patterns.I don't see anything in the overall trends to be stressing about. You appear to have 15K on the OE tires, which are not good MPG tires to begin with. Your MPG trends are well within what's expected with changes in tire performance. Bump your pressure 2-3 lb and start looking for a decent LRR tire if you really feel the need to boost MPG.
Crpriusv, I agree with RD. Your tank averages look on par and consistent with your notes for each tank. I don't like using the instant mpg display for comparison because it's too volatile. In my case, even short trip (local-not long roadtrips) averages tend to have a variance of +/- 3-5 mpg on the same route.
If you read my opening post I am looking for a reason behind the recent falloff in mileage which started immediately after my last service in late August. I am very satisfied with gas mileage up to that point...and yes it did follow expected seasonal trends...up to that point. Appreciate the comments though.
FWIW, there were any number of events in August that have nothing to do with your MPG. Your service visit is one of them.
I don't see any mysterious drops in your mpg based on your Fuelly fillups. You had a peak of 50.7 in August 29th but the rest of your fill ups average 45ish mpg with a variance of 2 mpg. Your peak of 50.7 makes the next fill ups look like a major decrease but the peak was not you norm. If you eliminate the 50.7, then everything else seems normal. When was this service in August?
Keep in mind that gas station pumps have different sensitivities triggering when they shut off. So mileage over many fill-ups and varying stations and pumps is what I watch and not an individual tank MPG. What if the trigger caused me to get .3 gallons less than the last fill-up? My mileage for the two tanks would seem different on fuelly but the overall mileage averaged would be more meaningful as the variations would tend to average themselves out over many fill-ups. I also ignore the display MPG as providing too much imprecision. I leave it on instantaneous just to give me some amusement as to the variation caused by how and where I'm driving. I annotate my fuelly entries to remind me of what kind of driving I was doing for that past tank as my driving can vary from in a hurry over 70MPH to cruising at 62 even over the same stretch of road. Maybe an equally interesting question is what did you do on your last tank that caused a change upward in MPG? You are getting better MPG than I am.
The service was on August 28, the day before that peak fillup. From that point on gas mileage just kept dropping for four straight fill ups. The latest fillup shows some recovery because I took special care to drive slower (< 60 mph) over this same route. I agree that the 50.7 mpg peak is probably an outlier, but there is still an obvious downward trend even when measured from recent averages. I am still hoping for an answer to my original question. Is there a setting in the motor ECU that, if altered, could impact mpg? Perhaps I should be asking this in the Technical Discussion forum?
