Hello All,

I have noticed a few things with my newly purchased used Volvo (2001 S40, 66,000), namely: at stoplights when ideling it sometimes surges/jumps; when ideling in reverse it sounds rough and recently spit out moisture from the tailpipe; sometimes when trying to accelerate quickly it revs too long before switching gears (it is an automatic). Some things to note, I have filled the tank three times - twice with low octaine and once with mid octaine; I changed the oil with semi-synthetic oil when I think previously it had used regular; I used a "fuel injection cleaner" prior to filling the tank. My questions are: (1) should I always be using mid to high octaine gas or is low/regular octaine ok? (2) do those fuel injection additives do any good or harm to the engine (3) Is their anything else going on that I should be aware of or is there any servicing that I should do now?

Thanks for any advice.

Sounds like the throttle body needs to be cleaned. A little moisture out of the tailpipe is normal. It is just condensation that occurrs when the warm exhaust gases cool in the exhaust system. I only use full synthetic oil in all my vehicles. I also run a bottle of fuel injector cleaner through every 3-4 months. If the car usually runs fine on the 87 octane fuel then you should be OK. I use 87 in my 02 S60 NA. You may want to talk to the dealer about the software update for the transmission. They updated mine and it took care of a very similar problem to what you described. Let us know how it turns out.

My thoughts,

Since you recently purchased your car you should know a few things.

Your car has turbo and is designed to run 91 or higher octane fuel. 87 octane won't hurt the engine but from my experience it will run barely average. You will also get more MPG from the high octane gas.

You should also spend the extra money and go with fully synthetic motor oil. Tests show synthetic blends don't offer much more protection than a standard grade oil. Turbo heats the oil up A LOT, and regular oils can't take the extreme temperatures. The few extra bucks you spend on good oil can save you thousands compared to the cost of turbo failure.

I agree with cleaning the throttle body to make it idle better. Also change your air filter.

Do you have a check engine light on?

You might also want to try disconnecting the battery for a few hours and seeing if that helps. The last owner may have driven differently than you and the computer adjusts to the way the driver usually drives. When I first got mine it seemed like it took forever to shift but once I beat it for a few weeks it actually shifts way sooner and takes off better.

Also don't forget to let your car idle for a minute or longer before shutting it off. You need to give the turbo time to cool off before cutting off the coolant/oil supply. It states that somewhere in the owners manual and I am sure almost everyone in here would tell you the same.

I am not sure about disconnecting the battery to reset the ECU, but I guess it would make sense(?)
I agree 100 percent with the other tips. Synthetic all the way, clean out your cars' throat, and always, always give it time to cool down after driving.

Good luck on your ownership, treat her well!