Mpg challange updates?

[redinjuns]

I can't help but notice the relationship between the price of fuel, and activity in this forum.
So Saturday I'm road tripping from here to Largo, in the diesel. There a couple places I could skip the Interstate for a few hundred miles and cruise some nasty 2 lane highways through the state. Which type of driving do you think will give me the highest mpg, 70 on the relatively straight interstates, or 55-60ish on these bent ass backroads with a little city mileage being the downside?

[supreams14]

Interstate

[Loren]

Yeah, cheap gas makes people complacent.

It really depends on the car and how you drive. For a lot of cars, particularly heavy cars, and particularly with "typical" drivers, cruising the interstate w/ the cruise set at 70 mph would probably be better because acceleration is minimized and the cruise control keeps them from varying their speed too much.

For lighter cars, especially if you adopt some of those "hypermiling" techniques (mainly gentle acceleration, and coasting wherever possible), keeping speed below 60 on the back roads would be better.

Example: My Yaris will get 40-44 mpg cruising at 70 mph. (usually about 43 if it's a constant speed, no headwinds, etc) If I keep the speed below 60, I can get 48-50. That's 20% difference in MPG just for slowing down 10 mph.

Try taking US-19 from N. FL instead of I-75. That's a great road for MPG until you get to about Crystal River. Not a lot of traffic, easy cruising at 60 if you want to, and you can spot most of the rural traffic lights and time them so that you avoid stopping and just coast down to maybe 35-40. If you're really light on the throttle getting back up to speed, you can actually GAIN mpg for every light you catch that way.

[redinjuns]

I'm taking the Jetta. It can't be taken as a direct comparison because of the obvious difference in shapes but in the Colorado I do a few miles a gallon better on the backroads. For instance here to ft. smith (interstate@70)is never better than 20/g, even losing 1200ft in elevation, but on a conservative trip out to Harrison (backroad@60)i can get 22/g same elevation. That Jetta did go 598 on 12 gallons before on I-75 on the last trip down, I think she did some drafting though.
Yes I should have taken better notes last time.

[Loren]

We drafted the Yaris behind a friend's race car trailer once and were averaging 53 mpg at 70 while doing it. Drafting can pay huge dividends, but is generally a dumb thing to do the way most people want to try to do it. You never know what the big truck you're behind is going to do, and the little bit you save on fuel won't pay for the new windshield or hood paint from the rocks you'll catch or the tire shrapnel when he pops a tire!

Try to do at least a 200 mile stretch on secondary roads that don't take you through big cities and get good numbers for that section of your trip. Keep the speed under 60 and a light foot and I bet you'll see something close to 60 mpg out of the Jetta.

[redinjuns]

Drafting can pay huge dividends, but is generally a dumb thing to do the way most people want to try to do it. You never know what the big truck you're behind is going to do, and the little bit you save on fuel won't pay for the new windshield or hood paint from the rocks you'll catch or the tire shrapnel when he pops a tire!

Try to do at least a 200 mile stretch on secondary roads that don't take you through big cities and get good numbers for that section of your trip. Keep the speed under 60 and a light foot and I bet you'll see something close to 60 mpg out of the Jetta.

Well it is my future ex-wife's car...

[FrodoGT]

Well it is my future ex-wife's car...

Well then your saving way more money than just mileage can account for

[FoxHondaRider]

I've yet to see better than 28MPG with my car. Rather sad when i was granny shiftin (not double clutching like I should be) lol and I still only got 28MPG I was expecting atleast 30. I would accelerate so slow and short shift but I guess it didnt help much.

[Loren]

Gentle acceleration is only half the battle. Keeping the speed down and (this is the biggie) not using the brakes unless you have to also make a huge difference.

On the highway, make use of the natural terrain. Even in FL, there are hills. Accelerate (gently) a little after the crest of a hill and get some coast time the rest of the way down and partially up the next hill. Resist the urge to force the car to maintain speed going up the hill, let it scrub off a few MPH.

In the city, it's all about looking ahead and managing traffic. I usually get better mileage in the city than I do on the highway unless I'm stuck in traffic that just plain isn't moving. As long as it's moving, you can do a lot of in-gear coasting and time yourself to the lights and the traffic flow so that you rarely need to use the brakes. Remember that in most modern cars, coasting down in-gear uses no fuel as long as the revs are above 1200-1500. Use that to your advantage. Rather than neutral-coasting up to the light and stopping for 30 seconds, coast-down in gear and use most (or quite often all) of that 30 seconds decelerating using no fuel rather than sitting at the light idling. And, if you're lucky, you'll manage to not come to a complete stop before the light changes and traffic moves, so you often won't have to start from a complete stop, thus saving more fuel.

Of course, some cars respond better than others. My wife's MINI Cooper is rated at 31 highway, and it's all I can do to get 34 out of it. I find that frustrating, but part of it is probably due to the automatic transmission.

I'm back to "playing the game" again lately. My last tank was 42 mpg average and included about 8 autocross runs. Just filled up today, no competition this month, so I'll try for... maybe 46-48. So far I'm at 48+. And lest you think that's just the car... it's EPA rated at 29 city and 36 highway.

It's definitely "gas mileage season" for me... no AC makes a significant difference in my car.

[FoxHondaRider]

Gentle acceleration is only half the battle. Keeping the speed down and (this is the biggie) not using the brakes unless you have to also make a huge difference.

On the highway, make use of the natural terrain. Even in FL, there are hills. Accelerate (gently) a little after the crest of a hill and get some coast time the rest of the way down and partially up the next hill. Resist the urge to force the car to maintain speed going up the hill, let it scrub off a few MPH.

Oh I'm the downshift king lol people complain at my downshifting because obviously it makes noise and most arent used to it. At my rate, I will get 100k miles out of my pads lol I downshift like I'm in a road race and sometimes heel toe. I've heard all sorts of dumb comments on my downshifting like "downshifting kills your valves", "downshifting ruins your clutch", "thats not good for the motor", and "why dont you just ride the clutch of put it in neutral". Theres times I have put it in neutral and braked and its like WTF am I going to stop? The engine braking by downhiftingrequires so much less of actual braking to slow down. I thought this could also be my problem with MPG. And thats exactly what I do with using natural terrain. I will accelerate downhill to carry more speed over the next and maintain my speed rather than pushing the gas more to maintain the speed on the hill.

[Loren]

You're downshifting to decelerate. What you want to do for economy is downshift merely to keep the engine revs up. As long as the revs are up, the ECU shuts off the fuel injectors and you use no fuel. You really don't want to get into "compression braking" to decelerate. The whole point of the exercise is to COAST as much as possible and use the DFCO (deceleration fuel cut off) feature of your ECU to use NO fuel while you're doing that.

SOoooo... it's actually better to stay in a higher gear so that the load of the engine slows you down LESS and you can coast "free" for a longer period.

It makes more sense when you can watch a real-time MPG display and see what's going on. It goes something like this: (typical modern small 4-cylinder)
Gentle acceleration from a stop = 14-18 mpg
REALLY gentle accel from a cruise = 25-30 mpg
Cruise = 30-40 or more depending on the car and the speed
Lift throttle coasting in gear above 1200 rshared_pm = infinite mpg (zero fuel)
Idling at a stop = 0 mpg!

Obviously, it is to your greatest benefit to extend the amount of time you spend coasting in gear vs doing anything else. Every fraction of a mile you spend coasting in gear is "free".

Watching the Scangauge in my car, if I'm on a typical city trip (under 25 miles total), every time I lift off of the throttle for 2-3 seconds, I gain about a tenth of an MPG for that trip. I lose between .5 and 1 mpg every time I stop and wait at a light, and about the same if I have to make a sudden stop (no "free" coast down to build up some mpg) and accelerated from it.

So, if I make a 20-minute trip and figure that the EPA rating on my car is correct... I'm starting at 29 mpg. If I can do a 3-second coast every 15 seconds or so, I've gained 80 tenths or 8 mpg just from that. Puts me up to 37 mpg. Of course gentle acceleration is good for an easy 10% in my car, too, so there's another 3 mpg. This is how I can easily get 40 mpg in the city in my car.

You're doing good by trying to not use the brakes, but if you're downshifting to slow down, you're STILL wasting momentum. Try to conserve and use as much momentum as you can.

Just got back from lunch, about 18 miles each way. Even with shitty holiday traffic, I managed to trip 49 mpg on the way there and 51.2 on the way home. Tank average is over 49 right now.

[redinjuns]

Um ...so I ran it like a banshee and the tanks came out as follows
Filled it up in Ft.smith
Ran it down I-40 for 248.6m/5.3g=46.9mpg; some of that ended up on the fender, I just didn't believe it was full.
Took that tank down 78 to Prattville, Al. Might as well have been Interstate 70 mph limit for 318.7g/7.2g=44.2mpg.
Next fill was 129.0m/2.7g=47.8mpg don't remember where the fuck I was.
Got here and ran the last tank out running all over the place 496.1m/11.5g=43.1 mpg.

1192m/26.7g= 44.6mpg and I was in a hurry. Might take it a little slower on the way back up...but I doubt it.

[Loren]

Gotta love a car that can return that kind of MPG even without trying!

[redinjuns]

Well it's an auto as well, I tried to see if it had the dfco as yours does, after 3 sec or so the engine pitch does change a little but it's not that noticeable at 70, no scan gauge so I dunno for sure. Halfway across the country on 70 bucks is pretty sweet though. Just got back so when I feel like freezing my ass off I'll get the new stuff up...hell of a headwind on 40 though so I think those are going to be the best numbers, car was alot heavier for the return as well, not much worse but not better.

[Loren]

Drove to Orlando yesterday and proved once again that my car is capable of much better mileage just running around town than it is at Interstate speeds.

Drove from Safety Harbor to I-275 on Hillsborough. Cruising speeds from 45-60, a few lights. 48.1 mpg average by the time I got on the Interstate. (and was still rising if I'd stayed in that environment)

Cruising through Tampa at about 60-65, mileage steadily dropped to about 46. Cruising a steady 68-70 through Lakeland, it dropped to under 45. Stabilized at about 44.5, but I got tired of driving 70 and kicked it up to 75. Then it steadily dropped again all the way down to 41.8.

On the way home, traffic was dense, so I was able to cruise 55-60 through much of Orlando and got the daily average back over 43. When traffic broke, I went with the fast flow at around 80 mpg most of the way to Tampa.

I'm convinced that Tampa > Orlando is slightly uphill, because even travelling faster, I managed to keep the MPG over 42 for the highway portion. Adding in another off-highway stretch on Hillsborough got the final day's average to 44 mpg.

I need to buy a TDI. I would if they were smaller. (Toyota! Where's my diesel Yaris???)