Acceleration vs. gas mileage

I have an ultragauge that I use to monitor the Taco when driving. I usually baby the truck as much as I can in city traffic but was wondering which is better.

When accelerating from a stop, is it better to go ahead and give it some more gas to get to the speed limit and then cruise or baby doll it up to the speed limit? When watching the instant MPG's it will usually stay around 9-13 when accelerating easy and then go up when the speed gets consistent at say 35 or 45. On the other hand, I can go ahead and give it some more gas and hit the speed limit quicker while the gauge reads 6-9 MPG's for less time. Maybe I am putting too much thought into it but I am always trying to max out my mileage.

 

i'd say baby it

 

I have not tried this with my truck, but with my mustang, I tried driving like a grandma for a whole tank. I kept it under 2,500 rpm for the whole tank and saw no improvement in my mileage. I think if you drive too easily and accelerate too slowly the engine is less efficient. There's a certain rpm range where the motor is most efficient, so trying to baby it and accelerate very slowly may not be the best tactic for improving mileage. Obviously, a vehicle is least efficient when it is accelerating and braking, so the more you can maintain a constant speed or coast, the higher your mpg will be.

 

Yeah, that is pretty much what I figured. I go easy but only to an extent and so far my tanks have yielded pretty consistent numbers. Still not worried about going out and having fun though.

 

I've found I've gotten better mileage when I give it some beans and get up to cruising speed faster.

 

It takes some time, and each truck is different based on gearing, tire changes, etc, but the trick is to find the "sweet spot" where your acceleration rate up to each designated speed is in the perfect power band and economy band. What does that mean? You will usually never find it because different driving conditions change this, and it also means you will spend lots of time trying to find it. In reality you are not making a huge difference in total average fuel economy either way. The difference is of course flooring it and accelerating up to a set speed will use a lot more fuel.

 

Quick little video from this weekend out at the local mud hole. I love the locker anytime mod.

http://s978.photobucket.com/user/ufboostedgator/media/My Videos/Video.mp4.html

 

I tried a few different methods (got bored on my daily commute so i tried to test this theory for a few tanks of gas). I found that babying the truck off the line doesn't really gain you anything. Don't pound it off the line, that will hurt MPGs but just take off normally. It makes a bigger difference what you do once your cruising, don't fly up to the light so you have to slam on the brakes and take off again, slow down ahead of time so you don't have to stop, keep a steady pace, not stop and go, etc.

 

I think that depends on the camshaft grinds and ECU controlled variable valve timing. Your Mustang's engine is likely designed to be the most powerful and efficient at high rpms, whereas my 2.7 is designed to do its best at low rpms.

 

I actually kept my truck under 2000 RPM and at or under 97 km/h before it would change a gear and go above 2000 rpm's. Got over 500 km's on 70L. Everything is stock.

 

Back in Auguest I put new BFG A/T KO size 275/70 17, I did notice a slight drop in MPG's, however the last two tanks of gas (two separate stations), I have gone from about 16 to 13 a major drop, tried driving slower and other stuff, no change, so may as well take off like a bat out of hell and grin while I watch my fuel gauge go down!

 

A taller tire will affect the odometer... The stock (31" on my Off Road) tires actually cause a false higher MPG reading. Once I switched to 32" tires, the speedometer and GPS were equal. Now an even taller tire will read that you have even worse mileage!

 

I went from the stock tires to 265/75-16 and my ultragauge average MPG is consistently exactly 1mpg off. I usually keep a small notebook in my center console and record almost every fill up. I recently transferred it to Fuelly and added it to my signature. The tire size difference, which has been on for the past few tanks or so is a miniscule difference in distance but my mileage has gone down a bit due to the mud tires. I have also GPS'd my speed indicated on the dash vs. GPS and it is right on.

 

Did the same with mine a year or so ago .... with pretty much the same result/analysis.

 

It is not just about slow acceleration to get better MPG although that is a big factor. You also have to get into the higher gears sooner without lugging the engine. Both must work together to get optimum MPG. In my 6 cylinder standard I get 24 plus on the HWY and around 21 in mixed driving. When I shift I only use 1st, 2nd, 4th, and 6th. I shift at 1500 RPM, except while in 1st which I run up to 2000 rpm.

In an automatic you are at the mercy at a preset shifting pattern governed by speed and applied torque that you designate. A light foot on the peddle will always get better MPG than a heavy foot regardless if you are accelerating or just cruising.

 

Yeah I noticed my miles driven was off, created a chart that shows how far I actually drove vs the OD reading, the funny thing is it was not a huge drop at first, just the last two tanks huge difference, wonder if they changed to winter gas in So Cal already. Think I am going to run the tank down in case I got crap gas the first bad tank! Love the tires though, would not go back to stock if they paid me to!

 

I have found I can get better mileage NOT using cruise control unless the road is absolutely flat. The instantaneous mileage displayed on my ScanGauge (6 cylinder 6 speed) drops much more using cruise on the interstate at 67-70 than with cruise off in both hill and rolling country. Have never ridden/driven a Tacoma with automatic, may not be affected as much. Have not noticed as dramatic a throttle increase in other automatic GM, Ford, or Tundra.

 

I shift at 3000 rpms and go 110km/h, with bed rack, RTT, bed slide, truck box, ARB bumper, 10,000lb winch with steel cable and All Pro rear plate bumper and I get 500+kms per tank.

 

Put the engine load % up on your ultragauge. Best average mpg when accelerating *should* hypothetically be anywhere from 80-90% load in the neighborhood of 2000 rpm. See what hypermilers do. Most engines have the the lowest BSFC in that general set of conditions. This gives lots of compression (high load), yet still closed loop (stoich), and lowest friction losses in the engine (which increases faster than proportionately with rpm), without lugging it.

On the V6 six speed, shifting at 2000 rpm with load at 85% is generally faster than typical traffic acceleration. On the four cylinder, I shift at 2500 rpm 90% load if in town and it's generally enough.

In practice, as long as the load is kept in that 80-90% area, there isn't much if any of a loss letting it spin up for faster acceleration. Can't remember where I saw the study on that. In that article it claimed mileage didn't drop dramatically until the engine went open loop (floored).

The worst thing to do is rev the engine too high while keeping the load down around 60-65%. This is what a lot of people think 'casual' driving is and it really wastes a lot. Same principle as cruising around in the V6 at 45 mph in 4th or 5th gear. If you use 6th to drop the rpm and get that load % up, the city mileage gets a LOT better.

IMHO

 

I saw this a lot too. If I could cruise at 55 mph at 40% load it would get around 25 mpg; if for any reason the load rose just a tiny bit to 45% it would drop so dramatically. I hated that - just a mild wind gust would hit the truck and suddenly it dropped from 24-25 to 15. Add in how much the cruise quickly varies the throttle input and there goes the fuel.

It's as if it changes the cam timing a lot or something at cruising loads. Thankfully the 4 cyl doesn't sweep the gauge like that, so to speak.