Set my baseline hiway

[99ParkAvenue]

After using my scII and unlearning my bad habits, I wanted to set a new baseline hi way mpg before I make any real changes to my car. I drove the I435 loop around KC after filling tank and then filled after I finished. I got 33.97 for the 92.1 mile trip. I'm pretty happy with that for Buick park avenue. Average speed was 60 mph. The car's only external change was i folded in the mirrors. Now I think I have a good data log for adding smoothie covers, fender skirts etc. Thoughts? Suggestions?

[AntiochOG]

A lot of things can affect your mileage, like rain, temperature, wind, tire wear, etc. That is why many people here will tell you to do A-B-A testing with any changes you make to test their effectiveness. Otherwise the results of your modifications could get lost or misinterpreted.

For example, you might add smooth wheel covers next week and go out and drive the exact same loop at the exact same speed. Then you go fill up and you got 33.67 MPG. Now you're bummed because your fancy new wheel cover seem to have made your mileage lower. But maybe it wasn't the wheel covers. Maybe it's 10 degrees cooler today and there is a 5 mph wind that wasn't there when you set your baseline.

With A-B-A testing you drive your test course without the wheel covers, with the wheel covers, then without the wheel covers again. Preferably back to back and with the exact same test conditions. It doesn't have to be for 90 miles either. If you're using your scangauge you could get accurate results driving a much shorter course.

[mcrews]

well done!
you might want to also record the time of day and temp. Also, that the engine had warmed up.
That way as you a-b-a test you can at least try to dupicale the external conditions
also was the a/c on or off.
a loop is a great test cycle because it covers the hills and the wind!
When I was in Sacramento I used a 10 mile north and a 10 mile south run on the free way as my base test.
nextI would increase psi to 40+.

[JRMichler]

Well said, Antioch.

To show how much difference some of these variables make, here is the Scangauge trip mileage for a 59 mile trip that I regularly make. Same route, same speeds, only two traffic lights that are almost never red, and same driving pattern. The only difference is temperature and wind.

31.8
36.5
33.2
34.2
38.8 69 degrees, no wind
31.2
25.7 This one had rain, snow, slush, and a head wind

I have got over 42 MPG on this route on a warm day with a tailwind.

That's why ABA testing is necessary to find if your improvements are really improvements. You are off to a good start. Getting 34 MPG when your average is only 24 shows that you have already learned a lot.

[99ParkAvenue]

Thanks everyone. My daily commute is 11 miles each way, and I have managed to get my tank MPG into the twenties. Rather good for a Buick in stop and go with lights. But even when I add a block heater, I dont have a long enough commute to really tert anything.

My hiway loop around Kansas City metro is 92 miles long and incorporates hills and flats. After spending one hour and 40 minutes yesterday, I decided to not run it back the other direction. I do agree it would give the best tangible proof if I did ABA but I just dont have all morning to do it twice. (Wife, kids, dogs, house - you know how that goes.) What I wanted to do was to see how well I could do going a safe 60 for the whole trip and to get a number to work from as I start modifying. Some of what I intend to do I dont expect to get a large gain from - like LED lights and Mobil1 - its a given that they will have little net effect on MPG. I expect to replace all the lights I can with LED equivalents, netting maybe .1 - .2 MPG due to the reduced drag on the alternator. Not enough to take a saturday morning to test ( or the ten dollars of gas.) Same goes for closing up body seams. Not enough gain to take a morning to test. But based on tribal knowledge from this site - I do expect it to add up a little bit at a time as I make changes. I expect more from smoothie wheel covers and side skirts, etc. Those specific things I will test. To add to the body of knowledge for us all, I will test each of those as distinct tests, so if I make 2, 3, or 5 little changes like the LEDs, I will rerun the loop and have a new base number before I test smoothies, skirts etc.

I was just kinda happy my Buick could get 33.97 on a 92 mile run when the Smart car is only rated at 35 or so on the hiway.

I am looking at the Buick as along term effort as it only just turned over 33k miles, so stuff like the LEDs will have time to add up. These Buick 3.8 are famous for going up to 300k miles.

[Frank Lee]

Yeah, The 3.8 is a good unit. GM really ****ed up when they decided to stop making it.