Relative Fuel Economy

[back2brand]

I have a 2019 GTI with a manual transmission and I typically run regular gas. Logically, I understand that the car will get less MPG cruising at 75mph compared to 65mph, but I'm curious about just how much of a difference that is. My gut feeling is that it's very minimal - maybe a half mile per gallon. Does anyone know for a fact how much the differential is based on some published source? Thanks.

 

[hans611]

From 75 down to 65 is a lot worse than you think, its probably more like 2-3 mpg.... or more....

 

[mrmatto]

That’s actually a pretty big difference in both air resistance and rolling resistance. At least 3 mpg difference, probably more, depending on your tires.

Consumer Reports actually tested this: https://www.consumerreports.org/cro/news/2009/09/tested-speed-vs-fuel-economy/index.htm

 

[Gray_Panther]

So the golf tsi would be the line to compare most closely to with our GTI’s?
Regardless, 45-48mph seems to be the sweet spot for maximizing mpg’s.

 

[OceanJack]

It's a pretty big difference as @hans611 said, I travel from North Jersey to Upstate NY traveling at 78mph I average 30mpg with 235 wide tires.
Tires will make a difference as well.

If I drove at 70mph, I'd probably get closer to 33/34 mpg.

 

[back2brand]

Many thanks for the responses - I guess my gut feeling was unduly optimistic. With $5 gas, I may give up some of that extra speed.

 

[SteveRedGTI]

Tires and conditions do have a lot to do with it. Mostly it's the driver.

My first longer trip was mostly interstate in the summer, almost 600 miles round trip. On the way over, since the car was pretty new to me, I rarely went under 75, and (sometimes maybe higher?). 37.5 was my mileage. Note that getting there was declining elevation. On the way back I got 36 or so. When I commute, it's all driving -related. Like most cars I've had, 70-72 seems to be the sweet spot. I get 35 going, 36 or so returning. Now the past two weeks I've averaged 32/33, and no, it wasn't at 70.

The real sweet spot for most vehicles are double-lane roads where 55-60 is the normal speed. Pavement has a lot to do with it, and our highways suck, I mean, suck.

 

[SteveRedGTI]

I can probably guess the answer, how many have started to put regular in their tanks?

I filled up with 92 non-ethanol yesterday and I was $5.76/gal

 

[bentin]

Doesn't running 87 cut timing and result in reduced efficiency? I'd be curious if the reduction in efficiency offsets the savings per gallon? I'd guess it's probably about a wash.

 

[SteveRedGTI]

Doesn't running 87 cut timing and result in reduced efficiency? I'd be curious if the reduction in efficiency offsets the savings per gallon? I'd guess it's probably about a wash.

On two tanks of 87, I noticed no difference at all in mpg. But no question the GTI runs more sluggish on regular. First time I noticed it was a ramp slightly uphill to the interstate. A little hesitation and definite sluggishness.

 

[Strange Mud]

for the newbie...an experiment I did a few years ago:

https://www.golfmk7.com/forums/index.php?threads/idle-hands-or-the-quest-for-a-480-mile-tank.373221/

also look at this about premium fuel. Note on of the test vehicles was an A3 so apples to apples

https://newsroom.aaa.com/wp-content...ium-Fuel-Phase-II-Research-Report-FINAL-2.pdf

 

[SRGTD]

Many thanks for the responses - I guess my gut feeling was unduly optimistic. With $5 gas, I may give up some of that extra speed.

Slightly off topic (apologies!) but $5 a gallon is a bargain!

In the UK our petrol is priced in litres, but I can remember buying it in gallons back in the 1970’s and 1980’s and I still sometimes convert to the price per gallon (old habits die hard ). Last week I paid £1.789 a litre which works out to £8.13 (US $9.80) a UK (imperial) gallon . An imperial gallon is larger than the US gallon, but at last week’s UK prices that would make the price of a US gallon £6.77 (US $8.16).

This week the average price of petrol in the UK is higher; £1.8659 per litre / £8.48 (US $10.22) an imperial gallon. That‘s the equivalent of £7.06 (US $8.51) for a US gallon.

Enjoy your cheap petrol guys .

 

[FJBGTD]

In percentage terms a car travelling on the motorway at 60mph uses 9% less fuel than when travelling at 70mph, and at 50mph I believe it was 26% less fuel compared to 70mph. This was in an article from BBC News last week on how to save fuel.

 

[Strange Mud]

Spoiler: Trigger Warning

We can use all our money saved to buy guns!

 

[PerceivedShift]

Slightly off topic (apologies!) but $5 a gallon is a bargain!

In the UK our petrol is priced in litres, but I can remember buying it in gallons back in the 1970’s and 1980’s and I still sometimes convert to the price per gallon (old habits die hard ). Last week I paid £1.789 a litre which works out to £8.13 (US $9.80) a UK (imperial) gallon . An imperial gallon is larger than the US gallon, but at last week’s UK prices that would make the price of a US gallon £6.77 (US $8.16).

This week the average price of petrol in the UK is higher; £1.8659 per litre / £8.48 (US $10.22) an imperial gallon. That‘s the equivalent of £7.06 (US $8.51) for a US gallon.

Enjoy your cheap petrol guys .

Our oil production per capita is also almost 3x that of your country...among other things. Up your oil game and enjoy lower prices.