MPG's on recent trip

Intech · Dec 5, 2014

I recently took a round trip to Florida 1700 total miles, and the mpg results were both good and disappointing. On combined back roads and city driving (through Baltimore and DC), I was getting between 55 and 61 mpg

. However, once on the open interstate, it dropped to a solid 49

. at between 70 and 88 mph, and I was using cruise control all the time. I had expected to get at least in the low fifties. Oh well........

DieselBruce · Dec 5, 2014

between 70 and 88 why would you ever expect low 50s?

BadWolf · Dec 5, 2014

At near light speed there may be a fall-off in fuel efficiency

Scoutx · Dec 5, 2014

+1

Speed feeds the need for fuel.

Intech · Dec 5, 2014

DieselBruce said:
between 70 and 88 why would you ever expect low 50s?

Because, before upgrades that got me into the 60's, I was getting 48

Intech · Dec 5, 2014

BadWolf said:
At near light speed there may be a fall-off in fuel efficiency

Actually Obe one kanobe, Luke and company, passed me a number of times

Intech · Dec 5, 2014

Scoutx said:
+1

Speed feeds the need for fuel.

So, I found out. However, going BELOW the posted speed is actually downright dangerous. Big trucks seem to be going about 8-10 above posted speeds and can cause some real problems when passing you

Enabled · Dec 5, 2014

Hmm, what mods do you have on the car? I've done many long trips, and I usually average 45 per whole tank or so when going 80-85. I've been tweaking more with the tune at partial throttle, and have gotten better tank averages, but never into the 50's consistently.

Intech · Dec 5, 2014

Enabled said:
Hmm, what mods do you have on the car? I've done many long trips, and I usually average 45 per whole tank or so when going 80-85. I've been tweaking more with the tune at partial throttle, and have gotten better tank averages, but never into the 50's consistently.

I don't remember exactly the injectors, I'd have to check. But I've got the EGR delete, 17/22 turbo, G60/VR6 clutch, 2.5" mandrel bent cat-less SS exhaust, with lo flow muffler and custom SS down pipe, RC3, Nokian WR G3 tires, which BTW upped MPG's by 3-5 around town, and a new TB by Oliver. Which, after it was done showed a very noticeable increase in power

puntmeister · Dec 5, 2014

49 mpg while averaging 75+ mph is pretty darn good.

As others have noted, mpg starts to drop above 65 mpg. Only so much can be done about wind resistance (and rubber resistance - higher speeds = more heat = softer rubber = more grip = more friction = lower mpg).

FWIW - these same issues apply to all cars. If you were driving a gas car, which normally gets 30 mpg - you'd be lucky to get 25 mpg while doing 75+.

The difference in absolute fuel consumption between 49 mpg and 60 mpg is actually fairly trivial.

Intech · Dec 6, 2014

puntmeister said:
49 mpg while averaging 75+ mph is pretty darn good.

As others have noted, mpg starts to drop above 65 mpg. Only so much can be done about wind resistance (and rubber resistance - higher speeds = more heat = softer rubber = more grip = more friction = lower mpg).

FWIW - these same issues apply to all cars. If you were driving a gas car, which normally gets 30 mpg - you'd be lucky to get 25 mpg while doing 75+.

The difference in absolute fuel consumption between 49 mpg and 60 mpg is actually fairly trivial.

I hadn't done any long distance driving for a while now, and when my mpg's jumped to the high 50's around town and suburbs, just by going to the Nokians (which BTW I had not expected), I think that spoiled me, and I expected the same or better at high speeds, which, if I had thought about it, and now realize, is practically impossible.

CourierGuy · Dec 6, 2014

Intech said:
So, I found out. However, going BELOW the posted speed is actually downright dangerous. Big trucks seem to be going about 8-10 above posted speeds and can cause some real problems when passing you

There's 2 types of people that'll drive under the speed limit. The "scared" ones, that should be on a bus, and the ones that do it intentionally.. intentionally for mpg, payload, mechanical issues or whatnot.

Driving slower than the traffic doesn't mean you just pluck it on cruise, and turn on zombie mode. You have to be somewhat aware of what is happening around you!

On 2 lane roads.. you will annoy people, and I don't really drive under on those. But 4+ lane roads, there's a spare lane for others to pass.

Yes, some truck drivers can be a bit arrogant.. but you just need to watch what's going on around you. Be conscious of the drivers merging on the hwy..

And if you really want to be a stickler, the speed limit is that, an UPPER limit. It doesn't mean you have to drive it, or speed over it, which would be "illegal". Heck, in Quebec, they post a MIN and a MAX.

I haven't seen anyone drive 60kph, the "min", when the "max" is a posted 100kph.

That would be a bit 'dangerous'

jhinsc · Dec 6, 2014

I remember living in SoCal/Orange County, there was one lady driving a red Toyota Corolla I saw several times on my commute home on the 405 freeway. She was always in the far right lane, driving 55 mph, and she ALWAYS had her flashers on. Whenever I passed her she always looked not quite like she was terrified but concentrating very hard, both hands gripping the wheel, and she wasn't old - I would have put her in her 30's at the time.

Enabled · Dec 6, 2014

CourierGuy said:
There's 2 types of people that'll drive under the speed limit. The "scared" ones, that should be on a bus, and the ones that do it intentionally.. intentionally for mpg, payload, mechanical issues or whatnot.

Driving slower than the traffic doesn't mean you just pluck it on cruise, and turn on zombie mode. You have to be somewhat aware of what is happening around you!

On 2 lane roads.. you will annoy people, and I don't really drive under on those. But 4+ lane roads, there's a spare lane for others to pass.

Yes, some truck drivers can be a bit arrogant.. but you just need to watch what's going on around you. Be conscious of the drivers merging on the hwy..

And if you really want to be a stickler, the speed limit is that, an UPPER limit. It doesn't mean you have to drive it, or speed over it, which would be "illegal". Heck, in Quebec, they post a MIN and a MAX.

I haven't seen anyone drive 60kph, the "min", when the "max" is a posted 100kph.

That would be a bit 'dangerous'

Well if you are courteous with other drivers, then that is extremely nice of you. Thank you.

It so happens that here in the wonderful South, people neglect to be so nice, and drive under the limit on the left lane (of a highway, etc) for miles and miles. Then they get upset with you when you try to go around a bit more forcefully.
Also they get huge butt-hurt when you pass them legally on open oncoming lane, especially if they're doing 45mph in the 55 zone, for example. I've had honking, flashing, them speeding up to not let you in.

It's a mess. Good thing that my Jetta is faster than stock now.

Intech · Dec 6, 2014

CourierGuy said:
There's 2 types of people that'll drive under the speed limit. The "scared" ones, that should be on a bus, and the ones that do it intentionally.. intentionally for mpg, payload, mechanical issues or whatnot.

Driving slower than the traffic doesn't mean you just pluck it on cruise, and turn on zombie mode. You have to be somewhat aware of what is happening around you!

On 2 lane roads.. you will annoy people, and I don't really drive under on those. But 4+ lane roads, there's a spare lane for others to pass.

Yes, some truck drivers can be a bit arrogant.. but you just need to watch what's going on around you. Be conscious of the drivers merging on the hwy..
And if you really want to be a stickler, the speed limit is that, an UPPER limit. It doesn't mean you have to drive it, or speed over it, which would be "illegal". Heck, in Quebec, they post a MIN and a MAX.

I haven't seen anyone drive 60kph, the "min", when the "max" is a posted 100kph.

That would be a bit 'dangerous'

I very seldom, on interstates, do the speed limit, I drive at the 85th percentile. When I've dropped below that, it's for a very specific reason, and on that particular trip, it was because of road fog, due to the temperature inversion at the time and places that I slowed down. Big truckers are immune to that effect, because they literally are above that in their cabs. I Know that because I have a CDL, and drove a big rig between contracts. I'm not a 'stickler' for anything, except a little courtesy, and until last year, drove about 80k miles a year. I imagine that would be close to 100km's in your area. As for 'illegal', that would be in the eyes of the police officer. As for my driving record, in the past thirty years, I've not received a ticket, or had an accident, not even fender bender

CourierGuy · Dec 6, 2014

Accidents don't happen on hwy trucking miles.

They happen in the city.

I've got one at fault accident.. More a fender bender.. No injuries.. In 2.7Mkm. In my defence, the girl was NOT looking where she should have been. My ego still hurts about that day.

Tickets? Wowzers, I won't admit publicly, but let's say this: a few cops knew me on a first name basis. That, and the words "facility insurance".

Young, dumb, and full of c+m. And fast, modified cars, on country roads.

MPG's on recent trip

Intech

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