Improving Gas Mileage? (also MAF discussion)

[Guest greenGT]

The gas could be different. More rich because of the hotter climate. Just something I heard. Like the need for summer and winter gasses. Death valley gas is the best and is the place every car dealer gets there MPG info on there cars, or so I heard. I got 28 MPG driving from the seattle area to san diego, I was going 75-85 too. I could be wrong on this?

 

jason

[Guest SmashPDX]

First guys: This is a cool thread, particularly with the detailed discussions of the MAF and all. When it's done I'm going to put it in the Archival Forum.

 

Re the venturi: Legacy777 & I have discussed the cone filter snafu before (I have a Weapon-R) and I have the "boggle" that folks have brought up. Where would one get or how would one make such a venturi? I was going to put some mesh in to deal with the turbulence but I couldn't find anything finer than what was already there.

 

Re the 32MPG '93 AWD Legacy-- two things. First, when you jump from the Legacy I (90 - 94) to the Legacy II (95 - 99) the mileage gets worse. If you're comparing a Legacy I and a Legacy II, you're not comparing apples to apples by a long shot. Second, the Seattle to Portland stretch is uphill going north and downhill going south. Both I and the significant other did the PDX-Seattle-PDX run in July for WCSS-II, me in my 95 Legacy LSi wagon (AWD, 2.2L, AT) and her in her 00 Impreza Sport wagon (AWD, 2.2L, AT) and the mileage coming home was SUBSTANTIALLY better, and different, from that going up.

 

PDX to LA there are some similar issues. Did the run in my Legacy in March, definitely got better mileage southbound than northbound and definitely noticed some issues with road grade.

 

Top issues for mileage in my book are the following:

 

(1) Driving style (coasting is better, and hard acceleration gobbles gas)

(2) Speed-- and hey, guys, my Legacy was pulling 27 highway average doing 70 - 75 MPH, without mods, after I got my alignment & tire issues dealt with. God knows what it would pull at 55.

(3) Tire inflation. Not just proper inflation, but consistent across the vehicle. If LF is 32, RR is 35, RF is 30 and LR is 29 you're going to have some weird issues. At the least make sure your fronts match each other, same for the rears.

(4) Wheel alignment. A lot of people pooh-pooh this and claim there's no way they could have an issue. But the fact is that if you're way off even after checking all the obvious stuff, and you're taking good care of your engine and driveline, your alignment is going to be the next thing to look at. My highway was at 24MPG and falling, even after 3 alignments by 3rd party shops, and then I finally got it into the dealer. Insist on a printout of before/after specs so that you will KNOW what you're walking away with.

 

Wheel alignment is particularly an issue if you've had everything aligned "right" only to go back and have them retweak to correct for drift-- which can be caused by tire manufacture (mine was). In such a scenario they may misalign the car to make the vehicle compensate for the tire-caused drift, which will make you happy but it will eat gas and isn't good for the vehicle.

 

That's it... hope this stuff helps. Let me know when the thread is "finished" and I'll archive it.

[Guest MailmanX]

All those points made perfect sense!

 

That 32 MPG I mentioned earlier was not an average, but just one tank. My son called me later today after doing about 85 mph through the valley, then climbing the Grapevine. That dropped his mileage for that tank to 28.

 

I think your point about the tire pressure and alignment were also excellent. I hadn't thought about mentioning those items since I don't tend to think of them in terms of a "tune-up". But my son's car just got (4) new tires, a 4-wheel alignment, and I made sure all tires were at 35psi (cold) before he left. So, the car is about as tuned-up as it can get right now. It's only downhill from here!

 

As far as I'm concerned, this thread is complete and can be archived. Anyone second the motion?