Anyone swapped diff ratios for better mileage???

[Robert K]

I understand everyone's debate that by having a taller final ratio, I might be using more accelerator to obtain the same performance. But, I'm not really after the performance. The big problem with the 535i's is that they were designed to be a "sports sedan". Now that's not a bad thing. But to keep the engine on boil for spirited driving, the lower rear end ratio keeps the engine revving fairly high on the highway. At 70 mph, I'm turning 2900 RPM's. I believe that to be my main problem regarding highway mileage. My uncle used to have an old 7 series (an '89 model I believe) that got around 26-27 MPG on the highway. I drove it once and remember the revs being quite a bit lower on the highway. So, my theory is that if I can drop my revs a little on the highway, I might be able to eek out a couple extra MPG's. But, that's only a theory. Of course the next question would be whether to go to a 3.91 or a 3.46 ratio.

I'll admit to running 235/45-17 Bridgestone Turanza LSZ's. Don't know how bad their rolling resistance is. I've actually told Tirerack that they need to include a rolling resistance figure as part of their testing. I personally would like to know which tires might provide better fuel economy. I believe Michelin is one of the only ones in the past who's advertised that aspect for certain passenger tires.

Well, I suppose I've got some figuring to do. Right now, the 535i is teetering on the edge of being sold and replaced by something more fuel efficient. I just don't believe we're ever going to see $1.50-$1.70 gasoline ever again. Because of that, I figure it's time to start driving something more efficient.

Grace and peace,

Robert K
1991 535i

[BobHarris]

You Americans don't know how good you have it.

Petrol is almost $8 a gallon here in the UK

All the best

Bob

[Kalevera]

Of course if you want to maintain possession of your baked confection with the contemporaneous ability to consume it, you'll figure out how to install a two-speed rear drive, just like in large trucks.

Haha... Excellent phrasing.


best, whit