BMW or Saab Convertible

Thanks for all your comments, keep them coming !

What sort of fuel consumption can I expect, mainly out of town, gentle (ish!!) driving, quite fancy a 323i, but want to make sure I won't be too much out of pocket, for company use I need 26mpg to break even, is this realistic?

Tony

The Saab will give you 26-32 avg highway and city. Some folks report

35 or so highway. I never get near that - I suppose because I like the incredible mid range torque of the turbo on the highway. :-)

I get about 26-27 on mainly highway driving in a 1995 Saab 9000, 30 mpg on all interstate trips. One good point for the Saab, it will run nicely on midgrade gas or even regular. It doesn't really like regular, but it will run on it. Just doesn't have the oomph it does on mid-range or premium. I believe BMWs all require premium.

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Live large. Spend a few pennies (on gas) and be driving a car you really want to drive.

Heck, I drive my cars for pleasure and don't get any money from my company for gas! Woo Hoo!

-Fred W

I don't mind spending a "few" pennies, but want to know how many first, I can't afford to subsidise my business use !

Tony

"apk1" haute in die Tasten:

Given the fact, that a BMW convertible is roughly constant in size and weight, a 2.8 litre engine needs the same power to move the thing as an

1.8 four banger. In general BMW engines are quite economical. As a rule of thumb I would say that the straight sixes burn 10-15% more fuel than the 4-bangers, but they are worth every drop of it.

Frank

While the lierature says "unleaded premium", remember that these cars are made to run all around the world. US Mid grade (89 AKI) is fine for most BMWs. The ECU's will retard the timing just like on the SAABs. The only difference is the SAAB will also limit boost if it detects pinging, so your loss of power when using lower octane fuel is greater in the SAAB.

-Fred W

The ECU that Saab has used for quite a while now, will back off spark timing, or boost, or both, depending on a number of factors. It's all mapped to find the optimal output given the current predetonation situation.

It'd be interesting to see torque curves for several engines, with different grades of gas, to see just how good they do. The only torque curves I've ever seen (for anything) don't show a comparison of that sort, but I'd love to see it. Anyone with a Dyno want to do a bit of experimenting?

You're right Dave. The curves you see are always done under totally optimum conditions. It would be cool to see some "real world" comparisons of what happens under lesser conditions.

-Fred W

Sure, provided you stay out of heavy city traffic. I think 20 mpg is a reasonable estimate for a 323iC with a manual transmission (>30 on the motorway if you keep the speed down).

The BMW's retarding of the timing will likewise reduce power appreciably. As to how that compares on a motor for motor basis, I don't think anyone does comparisons of power available during retardation.