cjf_moraga

No I am not about to bail out and buy a Prius... I am though casually curious about how "efficient" or economical it is possible to run the TT V12 engine... (On standard premium gas)

On a long freeway journey (HW 101) from the Bay Area to downtown LA last week I managed to get the number up to 21.3 mpg... but I just could not budge it upwards any further... same journey and route heading back was a little less efficient at 20.0 mpg... though it was mostly 100+ outside and the A/C was working harder... interesting in itself that the A/C seems to consume around 1.3 mpg more for a 20 F external temperature difference..

The only passenger was my teenage son together with some medium weight luggage in the trunk. Speeds were all in the 75 - 80 mph range and for half of the journey I had the car under the control of distronics, (which I love) but I could eek out a bit more efficiency under manual control - just an inconsequential 0.1 or 0.2 mpg though.

Anyone with a S600 (or even a S65) achieved any higher/better numbers than 21.3 mpg? I suspect that this number must be approaching the limit. (In normal driving - not resorting to hypermiling tricks)

Chris

WSH

Would guess that 65MPH cruise on a flat stretch of fwy (like 5 through Central Valley btwn the mtns outside SF and LA regions; or NJ Tpke from NYC-Phila; or the fwys around Chic) at 65-70F outside temp would yield several more MPG....

Also, IIRC, CA fuel mix entails some 1-2MPG less (in otherwise equivalent cars/driving) than cars w/NYC region fuel mix....

Esp in Eastern US where police hide in bushes to strictly enforce 65MPH, I suspect one's MPG is "forced" upwards....

Untertürkheim

What type of tires are you running? Real summer tires will give better fuel economy than all seasons or winters (usually).

It is interesting to note that the S550 can achieve much better fuel economy even though it has the same displacement, this is due perhaps to the extra 2 transmission gears and newer engine design?

cjf_moraga

Good question. My wheels are 19" with the original Dunlop 255/40 R19 Y rated tires that came with the car. I have them pressurized more firmly at around 34-35 psi. (cold)

Though the 550 and 600 are essentially the same displacement, it seems additional factors must include the two turbo-chargers and I suspect the additional parasitic loss/friction of any V12 compared to a V8.

Chris

Untertürkheim

If the tires are Y rated then they are summmer tires, I do not know what the standard tire pressure is for that size, but I would guess that 35 is probably the "high speed" pressure that would be specified.

I would guess that you have nearly reached the limit on fuel economy, the S600 has a rating of 23.5 for the German market, and I believe the car requires "Super Plus" gasoline, which translates to minimum 93 US. Since california is running 91 premium, and E10 instead of real gasoline, I would not bet on getting much better, if at all.

Untertürkheim

If the tires are Y rated then they are summmer tires, I do not know what the standard tire pressure is for that size, but I would guess that 35 is probably the "high speed" pressure that would be specified.

I would guess that you have nearly reached the limit on fuel economy, the S600 has a rating of 23.5mpg for the German market, and I believe the car requires "Super Plus" gasoline, which translates to minimum 93 US. Since california is running 91 premium, and E10 instead of real gasoline, I would not bet on getting much better, if at all.

trumpet1

Chris, everything you just said I can vouch for. I get the exact numbers you get and seem to drive the same way you do and I find this phenomenal for a V12. I really can't see why we are hit with such high gas guzzler taxes.

Oxygen

Talk about consistency.... I have a 2005 S600 with the same exact 5.5L V12 TT and the highest MPG that I can get is 21.3 mpg... It never goes higher.

I did the test on a flat highway, Cruise Control @ 72MPH, no passengers. 21.3MPG.