Actually, to my understanding, the drivetrains are Mazda in your fiance mazda3 the chassis is Volve, susspension is Ford with Mazda tweeks to their liking. And all three companys share the platform with each other in the...Euro Focus(here in '11), Mazda3 and Volve S4 but all three companys do different things/tweeks to make them individual.
I have read this many times but, I can't substanciate any of it. I have noticed that the brake master cylinder, calipers and such do say FoMoCo on them but this doesn't mean that the whole car is a FORD! Just parts of it as FORD owns some, oh let's say, 30% of Mazda.
OK, now that that's over, lets get to the tune up thing.
I blame fuel! My daughter has an '06 Mazda3 2.0 auto w/75,000 miles and never been tuned. She alway got and still gets very good MPG but, lately she too has been complaining that it has dropped substancially. As the matter of fact, we are all complaining about our MPG in all of our cars especially this winter as it was steadily cold this winter all the time. We actually check accurately our MPG and we never try to guess what it is like alot of people do.
Since the temps have climbed up nearing the 40's deg F we have all noticed that the MPG is also climbing slowly but nothing great. We have had a couple of weeks of warmer temps and our MPG in all of our cars is still lower than we all remember at these temps.
Now, I don't know how cold it gets in NC during this time of year(winter) how many mountains she drive through nor do I know what your fiance was getting as a baseline MPG. Has your fiance just started complaining or has she been complaining all season long as my daughter has??? Especially from Jan-present. Has your fiances' driving route or style changed at all???
My daughter's mazda3 usually gets 33 MPG city/mixed driving and over 40 highway and highway only. This winter her MPG dropped down to 25 city/mix(5W20) and is climbing back up slowly as we're entering Spring. The EPA on this engine is 26/34 w/auto tranny and 28/35 manual tranny. She does better just because of good driving habbits, a bit of expressway driving(one on ramp to another off ramp) and good engine tune. From NY to Chicago, over 40+ MPG but, Your mileage may vary(YMMV)!
Check tire pressure, hanging up brakes and anything else you can think of that may be causing lower MPG all of a sudden. My daughter was actually getting better MPG with 5W30 than with 5W20 and the engine is just a bit quieter too.
Those 2.0's are sweet little engines. Drive it yourself and see if you feel anything amiss. They're smooth everywhere and if you feel anything rough, there may be a slight issue with the engine.
I did install new tires prior to winter and her MPG has never been the same but, that was in NOV'10 when the temps started to drop anyway so, it was hard(er) to measure. Although these tires are not supposed to be a high rolling resistance tire, they'er not an low rolling resistance(LRR) tire either. The previous tires were worn and hard maybe causing the HIGHER MPG. Were new tires installed recently on your fiances' car???
This is all I can think of right now!
I think MPG will climb as temps rise.
