Do MPGs increase after "break-in"?

[stbal]

Do cars gain MPGs when "broken in"? I've got a brand new Hyundai Elantra and have so far been disappointed in the MPG despite going to great lengths to maximize mileage (however I note that my results are right at the median for my particular model on Fuelly). Nonetheless I'm unhappy, especially with the hwy mileage which is not coming close to what I expected. Question: Can I expect better results after 4-5K miles on the odometer? Do modern engines/tranmissions "loosen up"?

[BDC]

They do indeed, however not by the discrepancy you are experiencing. I have logged mileage on my Scion since new, and the average of the first 10k miles was somewhere in the 5 to 10 percent range less than the following 70k miles. But 5% of 31 is only 1.5mpg, and that's only a small fraction of the difference between your mileage and EPA.

I would like to give Hyundai the benefit of the doubt that their "38mpg" car can possibly do 38mpg. I'm going to go out on a limb and guess that you live somewhere where people drive really stinking fast on the highway, or you have a lot of red lights on your highways, or you tailgate and slam on your brakes a lot or something along those lines. Care to give us some detail on your typical "highway" trip? Average speed, distances between lights/stops/traffic, how often you have to hit the brakes on the highway, etc. This information can often tell you why your mileage is the way it is.

[stbal]

Well, my Hyundai is one of those that just had their MPG claims downgraded, by 2 MPG in my case. So now I should be getting 37 instead of 39 on the freeway. Unfortunately I'm barely keeping it on the happy side of 32. I should also note that my 2002 Camry, rated at 32 HWY, has for over 110K miles hit that figure on the nose. So why should I be struggling in a car that is a) newer, b) lighter, with c) a smaller engine and which d) advertises itself as a fuel-sipper, to match a 10-year old midsize car? Let's also remember that with the Hyundai I am trying much harder to maximize my MPGs. If I drove it the way I drive the Toyota I shudder to think what I'd get. The Hyundai ought to be capable of 37 HWY w/o me going to full-blown hypermiling to get there.

Two weeks before buying this Elantra, I drove a 2012 Hyundai Sonata 1800 miles through Colorado, Wyoming and South Dakota. Consistently got 34-35 MPG while cruising at a steady 70 MPH; hit nearly 37 on one tank. You can imagine how excited I was about what I'd get from my smaller, lighter car from the same company. Still waiting.

I live in the Baltimore area. Plenty of rolling hills on the highways, but not what you'd call mountainous, at least w/in 50 miles of Charm City. Usually a lot of traffic but my greatest chunk of highway miles have been late nights/early mornings w/o significant traffic.

I'm sure there are a few things I could do better to maximize the MPGs, but I'm already observing so many of the most important rules that I frankly can't believe anything more than another 1-2 miles is possible. And again, my consistent past success at hitting the EPA ratings on my Camry (and on a Nissan truck I used to own, as well) tells me that the nut behind the wheel is not the problem.

I am open to any further suggestions, even though I'm clearly frustrated. TIA for any ideas you've got.

[Draigflag]

One of the boggest problems in America is that a lot of people drive autos, traditional old school heavy poorly geared that not only have higher fuel consumption, but higher emisions than thier manual equivelants. Autos drive themselves really, the driver has little input. With a manual you can skip gears, pull away in second, coast and perform many other fuel saving manouvers that autos dont allow.

As regards to the engine breaking in, yes, I used to get 27 to 33 MPG when mine was new. Seem to be averaging closer to 40 MPG now with almost 50,000 on the clock. Think it felt proper broken in at around 30,000 miles.

[crvRider]

I recently purchased a 2012 Honda CRV and I also wonder if the gas mileage will improve after a few thousand miles. I am delighted thus far with my average of 32.5 MPG. My actual mileage is 1 mile per gallon better than the trip computer indicates and if mileage improves even more that's a plus. Most of my driving is on a winding and hilly road. I have learned to time my speed so that I seldom touch the brake. Braking is the biggest waste of gas. All of the energy used to achieve your speed is wasted when breaking. Hopefully as the miles add up on the CRV the MPG will improve by another 1 or 2 MPG.

[bates]

stbal, I have had similar experiences to BDC with slight improvement as the engine breaks in and the rings seat and loosen up but as he states gaining 5-7 mpg from a 32 mpg baseline isn't likely as that would be roughly a 20 % improvement and frankly from a mechanical standpoint your engine would be seized at this point if it was that much too tight.

One other thing to check is the gas and ethanol blend that you might be using. I'm guessing that the Greater Washington DC area has significant AQMD regulations and requirements. You might try a tank or two from an outlying area in the hopes that there is less or even no ethanol in that gasoline blend. I know that my car gets 15-20% loss in mileage now that Southern California has gone to a mandatory 10% ethanol blend year around. I used to just suffer that using the "Summer Blend" until about 6 years ago when the AQMD out here changed the rules and outlawed MTBE and forced the E10 gasohol on us. When I drive out of state to Arizona and Nevada several times a year I get significantly better mileage, often 20% or so better by shopping for gasoline with little or no ethanol in it, especially in Arizona where it is realitively easy to find. That is in the same car, with as you said, the same "nut behind the wheel" etc. It might be worth a try to see what happens.

[bates]

Stbal, you mentioned in your follow up post that the rental was driven out of state and again this could very possibly explain the increased mileage with a change in ethanol content for the Colorado, Wyoming, and South Dakota areas.

[BDC]

I used to have a map of what fuel formulations were required by law based on the geographic location, but I seem to have lost it. Maybe Google could help you find one.

Regardless, the actual energy content of E10 is only 3 percent less than regular gasoline. I have experienced as much as 8 percent drop in mileage when using E10 versus pure gas, but even that only in certain vehicles (others there is no statistical difference between the two blends). A twenty percent drop using E10 is outlandish by any stretch of the imagination. This is absolutely not the root of your problem.

[stbal]

A hopeful note: Yesterday put 100 mi. on the GT after a fill up, 95% of miles on the freeway (I-95 between Baltimore and DC). Mileage according to car readout was 36.4. My car overstates the actual MPGs by 2.8% (I've been tracking it), so that 36.4 is really about 35.4.

This is by far the best hwy mileage I've gotten so there is some hope. The only discouraging note is that it required minute attention to my acceleration/coasting while driving. Not sure I'll be able to maintain that level of technique on a much longer hwy trip. Hopefully those techniques can become ingrained.

[MontereyTDI]

Engine break-in will help but don't expect anything too pronounced as outlined above.

I've recently been amazed by how much my mileage has gone up by studying and practicing fuel saving techniques;

- Speed limit plus 5mph is where I set cruise on highway trips

- Tires are at 85% of max pressure allowed on sidewall

- Practicing using the Decell Fuel Cutoff Valve which is starting to become second nature.

- Still doing an Italian Tune-up once a day to keep the turbo and pipes clean.

- Best so far is 48 and shooting for 50 mpg