Getting low(?) gas mileage.... 22mpg highway

Just ran down to NYC from Boston twice in 2 weeks.

 

Each time, I reset the trip computer, and got 22mpg for highway portion of the trip. (About 200 miles.)

 

I have the cruise set at around about 75-80 almost the entire way. I really don't engage in any sort of insane accelerating, just a few passes here and there.

 

Is this "low" mileage due to the speed I am running at? IE- If I drop down to 65 will I be heading into the 28mpg range?

 

22mpg seems absurdly low to me for some reason. Like an SUV!

 

Yeah that seems low to me too. It could be a few factors and one is surely that you are running close to 80 MPH. When I set cruise that high I see my HWY MPG go down significantly over even 70 MPH.

 

Also maybe there are a lot of hills on that drive and the uphill climp hurts you even more trying to maintain 80 mph. Bad gas? Wet Roads?

22mpg is high for an suv. The new hybrid highlander boasts something like 24mpg highway. you are right where you should be for your speed

Try setting your cruise to 65-70mph-ish. I was around that level and getting almost 28mpg last night on the highway (mostly flat terrain).

Yeah that seems low to me too. It could be a few factors and one is surely that you are running close to 80 MPH. When I set cruise that high I see my HWY MPG go down significantly over even 70 MPH.

 

Also maybe there are a lot of hills on that drive and the uphill climp hurts you even more trying to maintain 80 mph. Bad gas? Wet Roads?

 

My trips from nor-cal to so-cal, about 320 miles ends up like this. CC set just right of 80=24 ish, just left=25ish, 75=26ish. I was planning to try 70mph on the way home but ended up flogging it for a return trip at 22ish. I'll try 70 when I'm feeling more patient.

Isn't 65+ starting to spool the turbo?

 

Or do I need to shaddap?

Your "normal" or "high" mpg readings are also important to know. Mine was running 21.5 mpg mixed driving until I had a cylinder compression problem fixed, and it won't run less than 24mpg now.

 

/t

I'm not sure how accurate it was but a recent report on NPR's Science Friday talked about fuel saving tips. The guest pointed out that wind resistance increases in proportion to the square of the vehicle's speed. So, small changes in speed result in significant increases in resistance. As a rule of thumb he said that going from 55 mph to 65 mph results in a 10% decrease in fuel economy. 75-80 mph is probably much worse.

I get about 22 MPG highway, too. I cruise at about 70 and the A/C is always on (Florida, you know.)

The car is highly speed dependent on good mileage. I usually go around 65-70 and I get around 27-28 but 75+ I see dramatic loses in gas milage to around 22-23.

mmm....acetone.... haha

I try to keep it around 65 or 70 when on the highway and get around 26 mpg, but thats usually with a trunk full of equipment, and some occasional traffic. I95 through CT blows. I believe around 80 mph is when the boost starts to build up and more fuel is being added to the mix.

I averaged 6.9 mpg after a total of 2 hours on a nearly flat road course yesterday, then got 27.6 on the 150 mile drive home doing 65-75 for the most part. YMMV (mine sure did )

My sedan gets about 2-3 mpg better than my wife's wagon does. I am pretty sure I am on the go pedal more often in my car than she is in her car. So maybe it has to do with different build date ECU's or the aerodynamic difference between vehicles. We drive similiar routes so it is not driving condition related in our case.

I would check the quality of the gasoline that you are using. Maybe higher octane gas or better quality gas will help ( timing retarded do to knock?). Also check your tire inflation pressure front and rear. Maybe your tires are underinflated or need to be inflated slightly over spec for the best gas mileage. I get about 24.8 MPG indicated on the trip computer, driving like a total maniac, ie over 80 MPH on the highway in my sedan with a lot of passing.

I consistently got 24 - 25 mpg at 75-80 mph and 28 - 30 mpg at 70 mph on a 3700 mile trip from Wa state to NM and back. I'd try different gas and check the tire pressure as well as others have already suggested.

I usually cruise at 75 mph here in Wa state on the freeways, any slower and I would be inpeding trafic. Since I went to Stage 1 1.15 I now see 21.5 mpg average highway. Dont get my started on the need of a sixth gear.

wind resistance increases with the square of speed, so mileage at 80 should be 66% of mileage at 65. The engine is more efficient at higher loads, so it's not that bad.

How accurate are the fuel mileage computers in our cars?

 

Try hand-calculating the MPG, and see what happens.

 

I know that the computer in my Audi is always 2-3 MPG optimistic. Maybe your car is pessimistic?

IIRC, doesn't the instantaneous MPG readout display a "- - -" rather than drop all the way down to "0.0" when the car isn't moving?

 

I think the average MPG that is displayed is based on only the amount of fuel consumed while forward progress was being made. If you do any significant amount of stop and go driving or just idling, then the average MPG will appear to be optimistic because the computer isn't counting all the fuel you "wasted" not going anywhere.

 

Example...

You drive 300 miles and it takes 16 gallons to fill the tank back up. Let's say one gallon of the previous tank was used up while the engine was running but the car wasn't moving. You calculate it as 300/16 = 18.75 mpg, while the computer does it as 300/15 = 20 mpg. Not wrong, just different. The car doesn't want to take the blame for you getting stuck in a traffic jam .

I've noticed that the av. mpg per tank does in fact go down on my computer if I've sat idling at a light/traffic jam, esp. if it's still pretty close to a full tank (i.e. above 3/4), when that sort of 'driving' would have a large impact on the ave. mileage overall. Overall, I've noticed the average mileage according to the computer is fairly accurate when cruising on the freeway at a constant speed w/o any hills, other that that, it's usually 1 - 1.5 mpg optimistic.

On my way back from Penn State, around 200 miles from where I am, I was going 75-80 the whole way, and got my record high of 28.4 MPG...I wasn't using cruise control, and have a 5MT. And I was in Post Gameday traffic for about 45 min (Idle/5 mph).

Pretty good mpg! I'll bet you're stoked about PSU football this year...

dam. i wish i could be getting 20+ mpg. im lucky if i break 18. average mpg is 17.5

now i consistently drive 65-70 on my 99% highway driving, and i can only muster 22-23mpg. what do you guys think of that?