I think manufacturers are focusing in the wrong areas to get mileage out of the cars honestly. While you guys are talking about how great a 3800 does on the freeway stock, do you know how much better they do with 30 minutes worth of tuning? I understand spending more time on the computer to "fine tune" the cars better might not be beneficial to them, but if they can improve the MPG on their cars by another 5mpg on the freeway, it seems like they would sell them a lot better.
My GP with XPZ cam, heads, headers, 2.55 pulley, 3.29 gears, intercooler, etc... averages 33mpg on the freeway at a 70mph cruise. Thats with a tiny supercharger pulley that robs a lot of power spinning that thing and a pretty large cam, and at that speed its spinning ~2300rpm IIRC with the 3.29 gears. While I did add some timing at cruise and lean it out a bit, it doesn't ever show even a hint of knock, so I figure a few more degrees of timing and a little leaner and I could easily get over 35mpg with it, I'm thinking 37-38mpg would be possible.
I took a stock L36, leaned out the fueling just a little bit (took it to 15.2:1 at cruising instead of 14.7) and added 5 degrees of timing just to start with to see what kind of gains I would get. At a 72mph cruise from Lima, OH to Holt, MI (~190 miles) I averaged 37mpg. Again in a GP with 3.29 gears. Thats on 87 octane! With some more fine tuning I don't see why 40mpg would be hard to get out of it, and if I tuned it for 93 octane it would probably be able to get mid 40'*. With like a 50/50 mix of highway/city driving this setup sees about 27mpg overall. Do much better than that in your economy 4 cylinder and I'll be impressed.
Thats why I'll be running 3800 powered cars for a long time. Can't really beat the mileage, especially for the power they make, and the other obvious reliability and easiness to work on.
1990 Maroon Grand Prix STE McLaren 3.1 Intercooled Turbo, 14.695 @ 94.49 on 12psi before cam/heads/etc.
1990 Bright Red Grand Prix McLaren 3.1 Intercooled Turbo, 14.819 @ 92.72, 189whp
1999 Grand Prix GT 9.75:1|K&N|160 tstat|No Ubend/Cat/Res|UD Pulleys|Ported M90/TB/Heads|XPZ|2.55"|Pacesetters|Stage 2 I/C. 12.442 @ 112.78
2000 Blue Bonneville SSEi Supercharged Gutted Airbox|K&N|3.4"|1.9'*|WP Pulley|Custom DHP|180*stat|41932'*|No Cat. 14.681 @ 94.80
2002 Dark Cherry Grand Prix GTP Supercharged & Intercooled
12.084 @ 114.38 w/1.743 60', 315.6whp, Fastest Stock Cam M90 GTP!
NOW XP CAMMED, 340.6whp with XP, stock heads, Gen 3 M90, 11.984 @ 115.84 w/1.750 60'!
Most HP Stock Heads Gen 3 M90 GTP!
2004 Red Monte SS Supercharged K&N|3.4 Pulley|1.9'*|180*stat|41919 plugs|3" dp|No cat/ubend|DHP|Shift Kit. 14.2 @ 98
GOT BOOST??? Friends dont let friends drive stock!