Maximizing MPG on highway

[kam327]

Originally Posted By: gman2304
Kam327, At 70 mph you're getting roughly 38 mpg, at 65 mph roughly 40 mpg, and at 60 mph you're getting roughly 43 mpg. Your graph perfectly illustrates what I said in my above post. The slower you go the better mpg's you achieve...but it needs to be done with safety being the primary concern and mpg's secondary. Thanks


Agreed.

 

[SwampSurvivor]

Originally Posted By: rslifkin
Originally Posted By: eljefino
It would be interesting if you could consistently prove the hills gave better MPG. The whole "pumping losses" thing.


Hills can help, usually in vehicles with big engines or not enough gearing. If it's downshifting on the hills, they're not helping.

In my Jeep, I'll get better mileage in mild hills than on flat ground, as long as I'm not gaining speed down the back side of the hills. Once the hills start getting steeper, mpg starts to drop off again.


Perfect Example: My Focus.

I drove from Albany NY to Syracuse NY and back on the Thru Way. Averaged 37MPG on the thruway. Non stop, highway, 65MPH.

Took the trip a few months later but decided to take US 20. That is CONSTANT hills. Not small hills, either. Car got 43MPG.

My car has DFCO. So, in addition to not using any gas going down the hills, I was building up speed that would allow me to use less gas to get back up the upcoming hill.

 

[asiancivicmaniac]

Are we to assume that the said car is currently in good mechanical condition, have had a recent tune up, and the tires are inflated to at least the recommended pressures?

If not, start there. Otherwise, you're really not doing that bad for a 17 y.o. midsize sedan.

 

[asiancivicmaniac]

Originally Posted By: lexus114
Originally Posted By: Miller88
Keep it at 55 or below.



Uh, maybe in Fl, but here you will be run over at that speed on the highway. Unfortunately


Maybe more like Ohio and Canada. You'll get run over doing below 65 here too. Heck, you'll probably almost get run over doing 70 in the far right lane.

 

[djb]

It really depends on the car.

Both my BMW e34 and e39 get better MPG at 70MPH than at 55MPH, typically over 30MPG. It rapidly declines above that speed.

All else being equal (it never is), smaller/shorter cars have an efficiency peak at lower speeds than larger/longer cars. A larger engine also moves the efficiency peak higher.

Some advice is just outdated. The "accelerated like a dozing turtle" advice applies to a car with a accelerator pump on the carburetor, not to a closed-loop fuel injected engine.

 

[jrustles]

Had the same car.

80km/h or 50MPH is the lowest threashold for OD/Lockup operation.
The problem with this car is that it only locks up the TC when there is so little torque being applied, than if it was left unlocked, it wouldn't slip much anyway. It really is a useless lockup program.

I wired up a switch to the lockup solenoid in that car and proceeeded to lug that [censored] everywhere I went. OD/lockup 25MPH crawling smoothly with a barely cracked throttle plate and I was getting INSANE FE. Lugging with wider open throttle yeilds no better FE though.

 

[sciphi]

Maintain a reasonable, steady speed, and keep it at 70 or below if possible.

If you're doing a long trip, it's up to you whether you want to spend more time or dollars on the trip. For most commuting, speeding wastes gas without saving much time.

 

[nleksan]

Funny enough, all my BMW's get better economy when driving around 75 then any other speed.

I agree with the post about payingat tention to traffic and not your exact speed. The whole hypermiling thing is dangerous, it is an absolutely guaranteed way to make everyone else on the road think you are a complete moron, and I cannot wait until the fad is over.

Maintain your vehicle, use the lowest ethanol content gasoline possible, USE YOUR BRAKES, and always drive with traffic (if you are holding people up, and know it, but don't stop then you deserve to be run over).

 

[BISCUT]

Originally Posted By: nleksan
Funny enough, all my BMW's get better economy when driving around 75 then any other speed.

I agree with the post about payingat tention to traffic and not your exact speed. The whole hypermiling thing is dangerous, it is an absolutely guaranteed way to make everyone else on the road think you are a complete moron, and I cannot wait until the fad is over.

Maintain your vehicle, use the lowest ethanol content gasoline possible, USE YOUR BRAKES, and always drive with traffic (if you are holding people up, and know it, but don't stop then you deserve to be run over).


New to BMW world and I noticed that with my E90. Around town not so good but on a hightway 70-80MPG it's happy with the gas gauge.

 

[Silverado12]

If I can, I drive at 65 mph. If the traffic is heavy, then I go with the flow or get behind (safely) a governed truck. I recently did 30 mpg in my Challenger at 65 all highway driving. On my commute, which is 60/40 highway/city, I get 22-25 mpg. Not too shabby for what it is.

 

[Vikas]

Originally Posted By: kam327
Here's my MPG curve carefully developed with a Scangauge. The slower I go the better. Of course this is a dual clutch automated manual with no torque converter.

This is very interesting graph. Could you tell us how many miles or minutes the car was at that steady speed before the sample was plotted?

There are some vehicles which have better city mileage than highway mileage but they are all hybrids. Is your car hybrid? If not, how do you explain your graph?

 

[TiredTrucker]

It was brought up about making sure one has a clean air filter. There has been testing done on both diesel and gas engines, turbo and NA versions. There is no appreciable economy difference between new, clogged, and severely clogged air filters and fuel economy, especially with newer computer controlled engines.

Here ya go....

http://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_26_2009.pdf

and

http://fueleconomy.gov/feg/pdfs/2013-01-0311_Diesel_AirFilter.pdf

 

[blackman777]

Highest MPG == When the engine is spinning 1500 to 1600 RPM in top gear (it varies car to car). That typically means driving between 40 and 45, but will also get you a lot of nasty looks and honks.

Another technique is to simply avoid using the brake. Every time you do, you waste energy. I find the best way is to set the cruise control at a speed of 60, so that people do not get angry at me. However they are still passing me, so that means I don't need to use the brake.

And I release the throttle early so I can just coast to a stop (when coasting the engine burns no fuel). In a Prius this will give you a braking score of 100/100 because it saves a lot of gasoline.

 

[nleksan]

Actually, with an automatic you will still burn gas, it's a manual where the engine cuts fuel. The torque converter is not able to function as a clutch in this regar. YYou will still get better fuel economy by not being on the gas, but the engine is still essentially idling.
Unless this has changed, I don't drive or own any automatic cars...

 

[RobertISaar]

GM automatic vehicles are entirely capable of DFCO and have been since sometime in the mid 80s... it isn't AS effective/last as long as with a manual trans, but it can still occur.

 

[supton]

Scanguage shows "9999mpg" while coasting in my Toyota Tundra with automatic transmission. It's much slower to go into fuel cutoff than say my TDi, especially when cold, but it definately cuts fuel.

 

[rslifkin]

Originally Posted By: nleksan
Actually, with an automatic you will still burn gas, it's a manual where the engine cuts fuel. The torque converter is not able to function as a clutch in this regar. YYou will still get better fuel economy by not being on the gas, but the engine is still essentially idling.
Unless this has changed, I don't drive or own any automatic cars...


Autos definitely do fuel cut on decel, but because of torque converter slippage, the minimum RPM for DFCO to occur is higher than in a manual.

 

[Clevy]

Originally Posted By: Silverado12
If I can, I drive at 65 mph. If the traffic is heavy, then I go with the flow or get behind (safely) a governed truck. I recently did 30 mpg in my Challenger at 65 all highway driving. On my commute, which is 60/40 highway/city, I get 22-25 mpg. Not too shabby for what it is.


With mos2 in my hemi I get 30mpg at 65mph with cruise set.

 

[blackman777]

Wow that graph was amazing.

 

[IndyIan]

Originally Posted By: nleksan
Actually, with an automatic you will still burn gas, it's a manual where the engine cuts fuel. The torque converter is not able to function as a clutch in this regar. YYou will still get better fuel economy by not being on the gas, but the engine is still essentially idling.
Unless this has changed, I don't drive or own any automatic cars...

You can't assume a manual even does a true fuel cut at normal rpms. The Focus needs 3000+ rpm to cut fuel totally and below that it actually uses less fuel coasting in N than engine braking. The Tracker does a true cut down to 1200 rpm but I still save gas on moderate hills in N as engine braking will slow it down too much.