What did improve the fuel economy for you?

[Cees Klumper]

fuel injector cleaner increased economy, which was already quite good, by about 8% on our two volvos, a 2003 S80 T6 and a 2002 C70 T5. The other determinant, at least on the highway, is sticking to 55-60 MPH rather than going to 70-75. Makes a huge difference (but I didn´t see it on the menu of choices). The T6 gets slightly better mileage, averaging around 28 MPG in mostly highway driving, than the C70 for some reason. This is on the lowest octane gas I can find. Incidentally my Honda motorcycle gets better mileage on regular than on premium, so better is not always better.

[MrAl]

Hi,

I noticed that not using the air conditioning reduces gas usage, although i dont have any actual numbers yet.
Not sure if anyone mentioned this yet or not.

Did anyone ever try to measure this difference in their Volvo?

[abscate]

1-2 mpg improvement without AC

There is a myth that putting your windows down causes more drag than AC, but it's a myth

[MrAl]

Hi,

Now that you mention it there was a study done at Stanford U that revealed that rolling the windows down does create more drag, but it's only significant (compared to AC) at speeds over 45 mph. So they are saying that at speeds over 45 mph it is cheaper to use the AC.

2 mpg loss isnt too bad i guess. It seemed like more but i never actually measured it. On the really hot days it's worth it i think.

[abscate]

There are many more studies that showed no such advantage

[tryingbe]

Drive slower and at steady speed.

[abscate]

Drive slower and at steady speed.

This is huge with my T5... Thread here.

https://www.matthewsvolvosite.com/forums ... pg#p367856

[sleddriver]

Aerodynamic drag increases with the square of velocity. Overcoming this takes a cube law force. Explains why the exotic hardware are powered by 600+ HP engines. Drag at such high velocity is just unreal.

[98v70dad]

I run my car in S mode and use 87 octane gasoline. I drive about 75 miles a day, mostly on the highway at 70 mph. On weekends my driving is mostly to the auto parts store, grocery store, short trips, etc. My mileage typically has been about 26 mpg. It gets slightly better in the winter. Lately my mileage dropped to 24.9 mpg, but I've been running the air conditioner at maximum speed which negatively affects mileage.

I've done a bunch of tweaks to improve my mileage and none of them made a noticeable improvement. I use an ultragauge that is permanently plugged in and my average mpg is 24.9 and it has stayed there all summer. The biggest impacts you can have on mileage are slowing down 20 mph, conservative driving habits and running your tires about 2 psi higher. Keeping the car tuned and a clean airfilter helps too. I've done all that and 26 mpg is the best I've been able to do. We have the 10% ethanol gasoline in Atlanta now which reduces gas mileage (thanks politicians) and anti smog summer blend which also seems to have a negative effect (thanks again).

[jvl]

On my new (to me) '99 V70XC I've been thinking about mods that can be done to improve aerodynamics. Driving it on the highway causes quite some wind noise, and probably also lots of resistance (= less MPG). Compared to my old Land Rover Discovery (headwinds make it feel like you're pushing your living room up a hill, by hand, while being hungover) it's much better but the wind noise made me wonder if anyone has experience in modding certain bumper parts, adding skirts, or whatever to reduce the sound and improve MPG?
From previous experience with the Discovery as well I am very sure that driving with under-inflated tyres and a roofrack really put a significant dent in your MPG.