I did my best trying to find posts to answer my questions, but I wasn't able to find much. IMO these forum searches aren't too great if you don't know the exact phrasing people on the forum use, so I apologize if there's threads already answering these questions.

So I just bough an 06 S40 T5. It was a one owner vehicle and still has the original engine and turbo. My main concern is treating the turbo and engine well so I can at least get a couple years out of them. The previous owner said most of his driving was on the highway, which I believe since the original equipment has lasted so long.

My plan is to do oil changes every 5k with full synthetic. I have a couple kits from Blackstone so I'll get the oil tested and see if I can go longer than 5k and how worn the engine is.

Overall the car's in VERY good shape, but I just wanted to know if there's anything in particular I should check or important preventative maintenance I should do. From some forums, I checked for oil/coolant contamination and watched and made sure it wasn't smoking on accel and deccel so AFAIK the turbo is at least currently in good shape. Also I've heard something about these cars having PCV issues, but I haven't been able to find out any details (searching PCV on this forum literally resulted in nothing). Is it something I should just replace the PCV valve if it's reasonably accessible? I've also read up a little on the thermostat/temp sensor issue, but I'm not having any issues with that at the moment.

Also this is my first car that's an automatic trans, so I wanted to ask if downshifting is bad for it? I'm used to driving manual so I've really gotten in the habit of it, I'll also do it on NA auto cars, but I didn't know for sure if downshifting would be bad for either the transmission or the turbo, because I'm really trying to baby this thing for at least a little while.

 

most important is to know if the timing belt/tensioner/idler has been replaced. the interval is 10 year/120K miles so your car should have had it replaced already. If not, that's priority 1. Going to synthetic is a good move. You may want to use a high mileage blend for your first change as it has some seal softeners which can prep for the more slippery oil. Some have suggested a seafoam treatment to clean out the VVT gear passages.. You may also want to consider a drain/fill for the tranny fluid. As far as the PCV goes, you and do a simple glove test - latex surgeons glove over the oil filler - if it inflates you have positive crank case pressure and should replace the oil trap in the PCV and check the hoses for clogs. If not, don't worry about it, just check from time to time. As to your downshifting an auto - not much point in doing so - but it probably won't hurt the transmission assuming you don't drop into low and overrev the engine, I'd just let the brakes do their job and let the transmission do its.

 

I think the leaking sunroof drains are the worst problem for the newer models. The clogged PCV system sucks but usually doesn't cause damage.

 

Ok, good to know. Should've mentioned the previous owner did the timing belt before selling it, he had the receipt and box for the new belt, as well as doing the trans fluid. You mention an oil trap, is that like a catch can? Thanks for the info!

 

Check to see if synthetic oil is required. If not, it is just an extra expense. The main thing on a turbo is to use the proper viscosity oil and keep it changed. That 5-cylinder engine goes all the way back to 1993 and is a real brick!

 

The PCV system is similar to a catch can. When it clogs the combustion blow by is heard through the dip stick tube as a whistle. Volvo has a program to replace them under dealer cost. It's not a recall as it's not a safety issue but it is a design flaw and Volvo recognizes it.

And I use synthetic oil exclusively in my T5. 144,933 miles and all is well. It's maybe 10 dollars a 5-quart jug difference but it's worth it IMHO.

My oil experience is with a Sears riding lawnmower I bought new in 1998. It had conventional oil when purchased but had a rather loud mechanical noise when running. After break in I changed the filter and put in synthetic oil. That engine was now quiet and ran like a top. It's now 2018 and that engine is still going strong. Maybe I'm just lucky but I'm sticking with what works.