What modifications were made to California-compliant 450 cars?

[smart-*ss]

I have been comparing mileage notes for many months with someone nearby who has almost exactly the same car that I do, his a 2006 and mine a 2005 450 ForTwo Passion Cabrio. The only difference is that his car is apparently U.S. compliant only, and mine is certified for U.S. and California. We both use the same brand of gas, have our tires inflated to 39-42 psi, have about the same driving habits

He consistently gets at least 10% better mileage than I do all the time, and just told me that he got 87 mpg on a highway trip. My best ever was just under 44 mpg, also on that same highway trip. My average so far (during this past year) has been 32 mpg.

G&K, who modified these cars for the U.S., told me that they did nothing differently for California cars, but I strongly suspect this is not true.

Does anyone know exactly what could be different between our cars that would make such a difference in mileage?

[rgaus]

There are no changes required to make a "450" version California compliant. They already meet California standards BUT, they still need the $1250 extra test because California did not "exempt" them. Here's the reason: In order to become exempt from California emissions testing, the manufacturer, G&K in this case, must pay a huge fee to cover "all" cars being sold within California. In G&K's case, that meant probably no more than 200 of the 1026, if that many. On a cost per car basis, it just wasn't worth it... so the only other option was to have each California sold car be tested at that $1250 price. The bottom line: California cars have same emissions settings as all the rest of the converted 450's. There is no "mileage" advantage for the non-California cars.

Now, to the problem. If you are fortunate enough to have someone else "near" you that is getting this great of mileage, ask if you can swap cars for a week. Here's why. Meet at a gas station between the two of you and fill up with gas. Both of you fill at slowest pump speed and remove pump when first click occurs. Note the exact location of each of your cars at the pump. Note the side, the direction of car, even the exact location on the concrete pad. All important. Then drive in your normal way for the next week. Meet at the same station in a week and fill up in the exact same fashion at the exact same spot on the concrete pad. You will then know if its the car or the driver that gets the better mileage. My guess is it's a little of both, but that will give you the answer. If he gets great mileage in your car, ask him for some tips or drive with him for a bit to watch what he does. There are ways to make your mileage climb that some folks are unaware of. Good luck! By the way, I have a customer in Kentucky that swears he's averaged 55mpg for the past two years. My 450 was always in the 40-45 range. Maybe the car, maybe the driver, maybe the type of trips.

His 87mpg is awesome, but the only true way to measure miles per gallon is through a scangauge or the method described above, where the same exact location is used between fills. I once added an extra gallon to my tank by just pulling to the other side of the pump. That would drastically effect the mpg calculations.

Ron Gaus, aSmartCar.com, St. Louis