I'm new to synthetic oils and would like to change. My Haynes manual tells me to change the oil and filter every 10,000 miles. How often do I have to change the oil and filter with synthetic oil? Do they always have to be changed at the same time, or do I have to change the filter without oil or vice versa? What about the auto transmisson? do I have to change that as well? I've just bought the car (97 855 1984cc 10valve 90,000miles) and intend to keep it for some time to come.
Thank you for any advice/information you may care to give

Comments based on 25 years of using and selling AMSOIL synthetics:

Yes, change to synthetics. I recommend using a good engine flush first (AMSOIL and BG come to mind). If you don't, or won't, flush, plan to change the oil filter after 2,000 miles, and the first batch of synthetic after 4,000 or so.

A good PAO based synthetic will easily last 10,000 miles in a sound engine, but I'd change the filter after 5,000 (or 6 months).
A non-PAO "synthetic" should be good for about 5,000 miles, maybe more if you take oil samples and find out for yourself.

You don't have to change the transmission, but it is a lot less expensive than buying a new one. Synthetic ATF will drop the operating temperature anywhere from 20-40 degrees F, and last at least 3 times longer than non-synthetic. Do a search and find the recommended do-it-yourself instructions.

Transmission fluid should be flushed every 20-25k. I use regular ATF.

Dick, I've been meaning to ask you. At the moment, I'm still at a limbo on whether or not I should switch from dino to synthetic, or just make my own blend. I'm finding conflicting opinions and suggestions from brickboarders, written manuals, and long-time Volvo mechanics alike:

One of my indi-mechanics, God rest his soul, told me to change the oil every 3k, or at least 4k, regardless of whether or not I use synthetic or regular oil: "Whatever you put in the engine will still have to come out of it."

In "The Gothenburg Bible," Paul Grimshaw writes, "Using synthetic oil, however, does not absolve the owner from continuing to change oil in accordance with the manufacturer's recommended interval as a minimum."

Then, brickboarders like yourself suggest that synthetic will last longer, protect better, and in the long run, prove to be cheaper than changing your regular oil every 3k.

In the meantime, I've decreased the oil change interval from 5k to 3k on regular oil 15w 40, until I can answer this question in my own terms. I wish it were clear cut, but it seems like the chapter and verse regarding oil change interval are open to more than one interpretation.

Regards,
ed850

Ed-
I have done oil analysis on the AMSOIL in my turbos. The oil is still suitable for use after 10,000 miles.
I can't tell you what other synthetics will do, but all should be able to go the recommended drain interval.

What's your driving habits like? Thanks, Ed.

Driving habits vary some. Used to put 30-35,000 miles on. Now I usually fly the longer trips and rent a car.
Currently, putting about 10K on my 88 Saab 9000turbo, city/suburban/some highway. The 85 Saab gets lots of short trip miles (wife drives it).
85 Volvo 245 turbo gets few miles, and they are varied but mostly within a hour of home.
Daughter puts on about 15,000 a year, mostly to and from work in downtown DC (think that qualifies as city).
Dodge van gets run to Richmond, mostly highway, about 220 miles round trip, maybe 25-30 times a year, and locally only to help in Rotary Fruit Sale/Rotary Memorial Day beer sales.
However, I do move about $8-10,000 worth a month through my garage, and can assure you it is used in almost any kind of driving you can think of!

Stop and go traffic for me during L.A. rush hour. Stuck in the 405 Freeway for at least a couple of hours to and from work, five days a week. At night or during the weekends, or when traffic clears, I'm doing at least 80 mph, sometimes even more, to get to where I want to be. It's hot during the summers and mostly warm the rest of the year here, with some rainy season. I also drive it to Las Vegas, San Diego, San Francisco and anywhere else in between on occasional trips.

I had 5w 30 regular oil originally, now using 15w 40 as I've mentioned. Now, contemplating on using Mobil 10w 30 synthetic year round with 3-4k interval.

BTW, I did purchase 12 quarts of Amsoil 5w 30. Thinking about trying that first instead of using it as ingredient to my home-brew synthetic blend for my brother's S90. We'll see.

Guys,
A sincere thank you for your replies. In my Volvo hand book on page 7:9, it says to change the engine oil and filter every 10,000 miles or once per year, or, every 5,000 miles or 6 months, if the car is used under severe driving conditions. e.g. extreeme temtratures, towing, prolonged high speeds, etc.
My Haynes manual says on page 1.2 to change the oil and filter every 10,000 miles or once a year, whichever comes first. If synthetic oil is so good, why should it have to be changed every 5,000 miles? Apologies if I appear dumb, but I'd like to be clear in my mind about this before I change over, as I've never used synth oil.
Again, thank you for your time and effort in putting my mind at ease.

The change interval would be due in part to oil breakdown (carrier oils in most synthetics aren't themselves synthetic), and also due in part to suspended micro-contaminants that don't get filtered out.

My synthetic oil drains much cleaner than the dino oils in my previous maintenance regimes ever did, and I run them longer - to about 7500 miles as opposed to 3000.

Could you go longer? Yeah, probably. But those oil ports in the turbo shaft bearings are awfully small...and I'd hate to clog one of THOSE up.
--
(98 S70 T5SE misc mods, mostly lighting) (92 940GLE)

75% highway.
--
(98 S70 T5SE misc mods, mostly lighting) (92 940GLE)

Stop and go traffic for me during rush hour in L.A. Then speeds of up to 80 mph, sometimes more, when the freeway is clear.

What's your driving habits like? Environment? Thanks, Ed.

I'd follow the manual that came with your car over the Haynes when it comes to oil change interval--they over simplified it ignoring factors such as severe driving conditions as you have mentioned.

That said, the 5k to 10k oil change interval recommended by the manual has all but become politically driven to boast that their vehicle requires less maintainance than others in its class. In a world where more cars are being leased, one never truly sees the long-term effects of taking shortcuts on maintainance. So, I'd take the manufacturer's recommendations as minimum.

However, don't get me wrong. Synthetic is superior to regular oil when it comes to protection of your engine. I would switch to synthetic and change at 3k-4k interval until I can get an oil analysis to see how far I can take it, but the OEM filter should definitely be changed at 5k, at least.

And remember, you're not going to hurt your engine by changing its oil more often than you should. Possibly your time and money if you don't mind, that's why I suggest the oil analysis so you don't second guess.

Regards,
ed850