4.0L RMP vs MPG

Ok I have read a lot on this and everyone tells you speed and MPG but tire sized and transmission choice have a lot to do with mileage. I recently bought a 06 DCSB with 4.0L V6 and a 6 speed manual transmission. I'm only getting about 16MPG. I live in an area that freeway speeds are 75 to 80 MPH and mostly flat. With the manual tranny and stock tires my RPM is about 2700 to 2800 when driving 78 MPH. My question is what is the ideal RPM for good gas mileage from this 4.0L???

 

I have read that already and 55 MPH around here will get you ran over. Reason I ask this question is the only reason the manual gets worse mileage is due to the short 6th gear meaning the RMP is higher. I plan on adding taller tires and would like to have a good idea of what RPM is best for this tranny/engine combo??? Speed means nothing when you look at the many differences of trucks.

 

Thats not true. lugging the engine will not get you very good gas mileage and is not good for the engine.

 

Anything after 65 mph, will give you shit for gas milage. Just because it says 75 mph speed limit. Doesn't mean you have to run 75.

 

Anything below 2000 rpm is where mileage rests. My 04 automatic double cab is at around 2300 at those speeds, those 6 speeds are geared way too high.

 

I'm a bit confused on what you are asking about.

Are you asking what size tire to go with to increase efficiency by dropping the RPMs?

or what to regear the diffs to?

 

1500 - 2000 RPMs seems to be the sweet spot for efficient cruising. Even though you get taller effective gearing, in my experience, bigger tires equal worse mileage in all situations.

 

say tire size. All Im asking is where is the sweet spot(RPM wise) for these 4L engines. I plan on lifting it some and going bigger tires. So im thinking maybe a 33" tire would put me in the 2200 RPM range at 75???... Just guessing with the lift and weight of bigger tires my mileage MIGHT not change and MAYBE even get better due to the RMP I will be turning at 75 mph.

One day if I decide to go 35" tire I will more then likely regear as well but for now let just say I want to know what tire size will net me 2100 to 2200 rpm at 75 mph?

 

Increasing unsprung weight will ruin your gas mileage. Decreasing unsprung weight will help it.

Bigger tires means heavier tires/rims = added unsprung weight = shit for gas mileage.

 

If you wanted good mileage you should of got a prius. The tacoma sucks on gas mileage no matter what you do.

 

The MT gets worse mileage than the AT due to a number of reasons, one being the OD in the AT keeps the RPMs low at freeway speeds.

I get 19-21 regularly, my RPM at 65 is around 2k. I find anything less than 65 to be good for MPG, the moment I get above 65 it starts droppping, rapidly after 70.

 

Like some had said already. If you want to get good mileage.... slow down. Just because other drivers are going 75-80 mph doesn't mean you should. Consider how high the MT is already geared, it is best to keep speeds at 65-70 mph for highway speed.

 

There's nothing wrong with someone trying to improve their MPG in any vehicle they drive.

Plus, if you want to shit on someones thread at least put an ounce into the creativity and come up with something more original and less cliche.

 

Just stating the obvious.

 

Sorry, I just realized you're 23 and still think everyone deserves to hear and read your words.

You should try being helpful, or not posting.

 

You're going to be constrained by what you can fit on the vehicle. I've seen guys fit 33" with some minor body work and a lift. 35s will take a bit more. They may not get you what you want either as the added weight will take more work to move. Also, as you eluded to, the lift will decrease efficiency as well.

If you go 33"s, you'll want skinnies (255/85R16 or similar). They'll save you on weight and rolling resistance over a 285/75r16.

 

My post was helpful. Tacomas don't get good mileage. Nothing to help that. Except trading it in for a prius.

 

Im just trying to gain info about the 4L tacoma engine. IF I was worried about gas mileage I would have KEPT my TDI jetta!!!

 

I understand didn't mine to sound like a a**hole. I've tried many things and can't really get over 16mpg. That's with stock tires 31s and 33s.

 

Out of all this I have gathered that keeping the RPM close or under 2000 RPM will net me the best MPG. I think after driving this truck for a week that anything under 2000 RPM there is no power at all. Now I just have to do the math to figure out what size tire to run to gain that kind of RPM. Reguardless of MPG the engine will be better off not running at 2800 RPM for hours on end. And for you guys that say slow down to gain better mileage. not going to happen here... I have had this truck for a week now and have over 1100 miles clocked on it... speed limit says 75mph I will be doing 80mph..... but I would rather my engine spin at 2100 rpm rather than 2800 rpm. Thanks for all the helpful information guys..