My dad has a 2006 Volvo S60 2.5T and we've been filling it up with regular unleaded since we bought the car almost two years ago. The manual does recommend premium fuel, but is there a noticeable difference (either short term or long term) between using premium vs regular?
We consistently get a combined mpg of 25-26, but most of that is highway driving so I would hope that it would a little higher than that. Would filling up with premium fuel boost the mileage a bit?

 

Usually yes it does get better MPG with premium.

 

it may make a tad difference but not much. I took a AWD s60 to chicago one time for volvo training (7hours) and it got about 27-28, i was runnin about 80-85 the whole way. with 87octane. the reason it recommends the premium is because of the Turbo.

 

27-28 mpg is quite good, especially considering it was the AWD version of the S60 and you were driving at around 80mph. This reinforces my question of why our FWD S60 2.5T, which gets driven most of the time on the highway doing 70mph, is only managing around 25 or 26mpg. Any thoughts?
There isn't a crapload of extra weight, we drive pretty efficiently, and there are only around 30K miles on it and gets serviced ,so there probably isn't anything mechanically wrong with it.

 

Just finished a round trip to Nashville using 87 octane. My highway mileage for the trip there was 28.1 doing 70-75 the whole way with AC. After a little around town driving and heading back to Memphis 2 days later, my average overall was 27.8 for the trip. I'll have to try out premium next time and see if the extra mileage pays for itself....

 

Thanks for the info twowheelin, let me know if you notice any mileage differences with premium next time you make your trip. It seems like the S60 really hates start/stop city driving, even a small amount will destroy any highway mileage achievements you've made.

 

Yes, andit probably doesn't help that the 2.5T torque feels so good when you lean on the throttle. [8D]

 

They recommend premium for the turbo.... does that mean in the long run you'll wear out the turbo faster or do any long term damage using regular verse premium or not really? How about for performance purposes, how much of a difference there?

 

It's not the turbo you need to worry about, it's the engine. With the increased compression pressure that a turbo puts inside the engine, fuel pre-detonates easier. If the piston is coming up when the fuel ignites forcing pressure down, the rods take abuse and may eventually break. Higher octane prevents the fuel from detonating before the piston is in the correct position and the spark plug ignites it. Ocatane is a measurement of the percentage that you can compress the fuel before it ignites.

There are no fuel saving additives in premium vs regular fuel. However, if the engine isn't running efficientlyvia pre-detonation, you'll see decreased hp and mpg.