best speed for mpg.

[Honda4life05]

What would be the best speed to cruize down the highway, to get the best mpg? Is it pretty much the lower the rpm the better? or does the engine have a sweet spot? something like a chevy 1500 V8. A couple of buddies were talking about this. what do you think?

[HondaPohl]

When I was driving the turnpike alot, I would cruise at 2000 rpm in fifth gear in my V8 mustang at get 24MPG. The less your on the pedal the less gas is consumed.

[NacsMXer]

I wouldn't say so much that speed is the most important factor. It's more so the RPM at which you are cruising at. Since cars come with all sizes of tire diameters and gearing combos, it's going to be different for each car/truck.

But a Chevy 1500 V8, in overdrive, i'd say it will get the best economy at around 1800 RPM's, which will usually be in the neighborhood of 65-68 mph. Start creeping on 2000 RPM and up, and it will start getting into the powerband of overdrive, but economy will start to drop. This is assuming a standard 4 speed auto trans and reasonable gearing....say 3:73's.

There's definitely a sweet spot for the best MPG's in overdrive/top gear but it will be below that gear's powerband or kinda in the "bog zone" if you will. Once you start getting out of the bog zone into the powerband (2000 RPM+), you will be in the sweet spot of that gear for acceleration, but not necessarily MPG's.

[Kickstarts-suck]

Originally posted by NacsMXer
I wouldn't say so much that speed is the most important factor. It's more so the RPM at which you are cruising at. Since cars come with all sizes of tire diameters and gearing combos, it's going to be different for each car/truck.


^^^^^ This

I have 4:10 gears so I have to keep it pretty slow on the highway if I want okay mileage.

[beastlywarrior]

the sweet spot on my silverado with a 350 is 55 mph buy at 65 im at 2000 rpm and 2500 at 75

[ProspectorJim]

once you go over 60-65mph youre fuel economy will drop drastically as the air resistance and the power needed to overcome it increases. This is especially true of trucks shaped like bricks.

[quad2xtreme]

For my Silverado 2500HD diesel, it is right when the auto tranny switches into overdrive...it is the slowest speed you can go while being in overdrive. Of course, I couldn't drive around at 50-55 mph. I do pretty well to 65 mph. All this holds true whether the truck is empty or pulling a 8,000 lb 8.5'X24' trailer with a flat front.

Sometimes I get stuck on country roads behind a car doing 45 and can't switch into OD. I definitely get worse mileage because the RPMs are higher in the lower gear.

[wilkin250r]

I cannot fathom getting your best gas milage at 60-65. While it might be true your ENGINE is most efficient at that particular rpm range, there is a tremendous amount of air resistance that requires power to overcome. Going from 55 to 65, the 10% increase in efficiency you get from your engine isn't enough to compensate for the 40% increase in wind resistance.

Your gearing is critical, so you have to be in your tallest gear. For those with automatic trannies with an overdrive gear, this is likely to be 50mph or more.

[derekhonda]

Ive always found that i get best fuel mileage in my last gear, at the lowest RPM. I also have sucky gearing, I think I hit my last gear right aroun 55 mph and as long as i keep it at 55 or 56 i get better mileage.

[fastredrider44]

You can be in OD and burn more gas than in 3rd at the same speed if you're not in the power of the truck. 55 is ideal for my 97 z71. 70 is ideal for my 02 2500hd. It all depends on motor and gearing. There is a huge wind resistance factor around 60 and up though.

[witech]

Ive checked my 04 avalanche on some long distance trips . One 800 mile trip I was limited to 55 to 60 mph .mileage was 22mpg with the wind and 19mpg against it with a snowmobile in back.

The other trip was 4300 miles hauling a quad and a bike on board. Speed was between 65 and 80 mph. It averaged 17mpg.

In my experience keeping my foot out of it , smooth gentle acceleration , and using cruise can yield benefits.
2 things that kill mileage are towing a trailer and speeds above 60mph. If you can get most of your load in the truck then do it and haul the lighter stuff on the trailer.

[quad2xtreme]

Originally posted by derekhonda
Ive always found that i get best fuel mileage in my last gear, at the lowest RPM. I also have sucky gearing, I think I hit my last gear right aroun 55 mph and as long as i keep it at 55 or 56 i get better mileage.

X2. If engineered properly, it is at this shift point when you have the best possible final gear ratio and should have adequate engine hp to maintain this speed for the best mileage. Anything beyond this starts to increase the burn rate of fuel quicker than the offset in fuel savings from arriving earlier and having you engine turned off.

[mx Eli]

Another thing to think about is that differant size tires can throw your speed GEARING and mpg off (only cus odometer is off) diesel trucks with 3.73 gears will run right around 2000rpm at 70 give or take alittle, now go to 3.55 gears and that goes to 2000rpm for 75-77.

In our 04 cummins, with the whole back loaded with quad, grill, cooler, tools, we can get 20mpg going 70mph on cruise. going 65mph we can get 21mpg. thats with 3.73 gears and 4 speed auto trans.

[fastredrider44]

Older vehicles tend to burn more fuel using cruise, and newer vehicles burn less fuel on cruise. In my 97, for best mpg, when I'm in the hills, I speed up on downhills and lose speed on uphills. On my newer trucks, just set the cruise and let it rev out to 5g when climbing hills.

[honda250xrider]

I would say the best MPG would be from 35-50mph in the tallest gear that isn't bogging. Wilkin is right the wind resistance is killer at higher speeds.

They did a test and the 2011 mustang was able to average 48.5mpg while traveling at 45mph on a oval track. I would have to say this is around the sweet spot for most vehicles.

[wilkin250r]

Originally posted by fastredrider44
You can be in OD and burn more gas than in 3rd at the same speed if you're not in the power of the truck.

Indeed, I've run into this problem. I've got a truck sitting on 40 inch tires, but it's geared for 31~33 inch tires. Whomever built this truck didn't regear it when they lifted it.

As a result, any type of hill I have to put the pedal to the floor and the truck will still barely get out of it's own way. It's still gutless because of the gearing, but it's sucking down the gas because I'm 100% full throttle. I took it over a mountain pass, speed limit is 40mph but I couldn't get over 25mph, and I averaged about 6mpg.

But unless it's a Mazda RX7, anything above 1500 rpm is generally in the "efficient" range of the engine. It's entirely possible a particular engine might be even more efficient at 2500 rpm, but it's usually only 10-20% better, while the corresponding increase in wind resistance is 40-80%.

[ZBlaster]

75mph is ~1,700rpm in my Titan on 35's. I can get damn good highway mileage as long as I don't try to pull 4g's getting up to speed, and as long as I'm steady with the throttle and not constantly speeding up and slowing down.