To get more FE...drive faster?

[PurpleHaze]

Hello all, I've been lurking but this is my first post.



Today I got my best tank ever-31 mpg

It's my highest. Second highest was 30 mpg. I've been keeping track of tank mileage for quite some time now. Here's the kicker. The 30 mpg tank was on a trip back from my brother's place, the 31 mpg tank just occurred on the way back to Findlay Ohio from Detroit. Both tanks happened at a rough average speed of 75-80 mph. You shoulda seen me slingshotting around semis...

Obviously this flies in the face of conventional wisdom that says you must drive slow to get good mpg. In fact, I've been driving like a grandmother lately for just that reason, and I think my best tank in the last 2 months has been 26 or so. Tonight I just wanted to get home yesterday, so imagine my surprise.

The car may have something to do with it. It's a 95 Buick Skylark 4 door 4 cylinder automatic.

Has anybody ever heard of this happening? I've spent the last 3 months staying at or below the limit on the highway, and now I feel silly.

[2TonJellyBean]

You should get a ScanGauge if you don't already have one. There are many variables when driving. With a ScanGauge you could easily test steady state MPG at varying speeds... or see short term averages for P&G techniques.

My Accord's steady state fuel economy is much better over 60 than under 50 MPH. I think it would do crazy P&Gs at a low average speed.

Anyway, your situation could have involved a 15 mph tailwind... maybe it was just more steady state, maybe it cleaned some carbon? It's tough to tell.

Does it have an ODBII port? It should...

[MetroMPG]

Originally Posted by 2TonJellyBean

My Accord's steady state fuel economy is much better over 60 than under 50 MPH.

Both in top gear? I find that difficult to believe.

[2TonJellyBean]

My Accord's steady state fuel economy is much better over 60 than under 50 MPH.

Originally Posted by MetroMPG

Both in top gear? I find that difficult to believe.

Yes, 5th gear.

I found it hard to believe as well... I would have sworn 45mph/70kph would have been the sweet spot for the Accord. This was with rolling terrain mostly using CC going up past Barrie and Huntsville from the Toronto area on the long weekend. It was most likely a combination of 4 people in the car and the rolling hills. The engine seemed to be below it's sweet spot when driving at what would seem to be great FE speeds.

Best speed seemed to be 55mph, but going anywhere from 60 to 65 didn't seem to reduce mileage much. In comparison, dropping down to 50 really increased consumption on any upward pitches. I wish that ScanGauge had an altimeter and could graph stored data like my Polar hear rate monitor / bike computer!!! ;-)

If I ever take the Accord on the 401 west of London where the road is pretty well dead flat forever I'll report back the CC sweet spot.

[MetroMPG]

Originally Posted by 2TonJellyBean

This was with rolling terrain mostly using CC ... 4 people in the car and the rolling hills.

Ah! CC. That changes everything. Particularly with the hills & added weight.

If you'd been using your foot & brain (if traffic had permitted), you would have greatly exceeded the CC's fuel consumption in those circumstances while maintaining the same average speed.

I can guarantee that on level roads at a constant speed your Accord gets better top gear fuel economy at 50 mph vs 60+, and better still at 40.

[2TonJellyBean]

Originally Posted by MetroMPG

(A) Ah! CC. That changes everything. Particularly with the hills & added weight.

(B) If you'd been using your foot & brain (if traffic had permitted), you would have greatly exceeded the CC's fuel consumption in those circumstances while maintaining the same average speed.

(C) I can guarantee that on level roads at a constant speed your Accord gets better top gear fuel economy at 50 mph vs 60+, and better still at 40.

(A) What added weight? We actually had an empty seat! You sound single... LOL

(B) My legs are cramped in the Accord - CC is my survival tool, so I'm very much guilty of trying to keep my feet out of it.

My brain however was very much FE engaged, much to the chagrin of my wife who was very relieved after the long weekend when "she" removed my ScanGauge from her car!

I had fun trying to find the sweet spot for CC in mildly rolling terrain. I was testing raw cruise and also assisted cruise (tap speed back on climbs). Tapping back had minimal impact when the approach speeds were near 50 or lower - unless it was a very small rise. Getting back to speed after seemed thirstier until it got closer to its sweet spot.

(C) I totally agree, but terrain and traffic are facts of life in most driving scenarios. Like I said, if I get the chance to ever test it on flatter terrain, I'd like to know what the optimum steady state speed is on flat stuff. Too bad that it won't be the Accord going to Florida in December... I can't believe I said that!!! ;-)

[VetteOwner]

no OBD2 started in 96-97 should be a OBD1 car

[Hockey4mnhs]

that might be becuase those were all highway that might be why your getting such high fe. Do you do all highway on those 26mpg trips?

[GasSavers_Ryland]

it could be that the engine is fully warmed, or that your automatic transmition is locking up at the higher speeds, and not alwas at lower speeds, or it could be the time spent behind semis, on long trips your tires warm up rasing the presure, your engine warms up fully, along with the fluid in your tranny, so it simply could be the long trip.

[PurpleHaze]

Yeah, there's LOTS of variables that could have made that difference. Next thing on my FE todo list is to select a good test course and run it at different average speeds (60-65-70 or whatever) just to get some science on the thing. I kinda wonder if the higher RPM/ speed gets the slushbox working more efficiently.

I'd LOVE a friggen ScanGuage, but I'm definitely OBD1. Exactly how do I get myself a SuperMID?