Mobil one is a fine brand. Amsoil is generally reguarded as the best. The oil costs a bit more (5.85 a qt) but Amsoil extended drain for a non turbo engine is 1 year or 25000 miles. Mobil one will not make any extended drain claims.
--
Paul NW Indiana '89 740 Turbo 108,000

I switched all our cars to Mobil-1 at fairly high mileages. No leaks appeared. They all used a little oil before the changeover; they seem to use a little bit less with the synthetic - hard to say. When I lived in Canada with some very cold winter mornings, I noted a real improvement in cranking speed and oil pressure gauge response with Mobil-1 5W30 compared to Castrol GTX of the same SAE rating. And GTX is a very good petroleum-base oil.

Now living in California with a lot of highway driving, I change the Mobil-1 10W30 every 10k mi. The 83's owner's manual calls for 7500mi changes in normal driving conditions for non-turbos. This was with the grades of oil available back then. Conventional petroleum oils are better today, and synthetics better yet.

Castrol changed their method of manufacturing their Syntec oils such that they are more of a super-refined (isomerized) conventional oil as opposed to the usual way of making synthetics using a base stock of poly alpha olefins. It's cheaper that way, but they didn't lower the price after they changed processes. (Surprise!) Mobil took them to some advertising ethics court to stop Castrol from claiming Syntec was a true synthetic, but the ethics police decided that "synthetic" was a fairly loose term and Castrol could still use it.
But I don't use Syntec.

--
Bob (81-244GL B21F, 83-244DL B23F, 94-944 B230FD plus grocery-getter Dodge minivan, MGB, and numerous old motorcycles)

For the first few 1000 miles, keep an eye on the oil level. When I made the switch in both my 90 BMW (@130k) and 240 (@155k), most of it burned of within the first few 1000 miles. There is a damn good reason for it, but I am not gonna get into it. Now, neither one of them burns oil...bimmer has 172k and 240 has 192k. I use any synthetic I can buy....well, as long as it is a brand name (Valvoline, Havoline, Mobil, Quaker...no NAPA brands :-) ). The past few changes I have been using BMW's synthetic. I get it from the dealer for $3.50/qt...thanks to my BMWCCA membership discount! It's a 5w-30 oil made by Castrol specially for BMWs....hey, if it's good enough for a bimmer, it'll be just fine for a 240. I do, however, add 75% BMW oil and 25% Mobil 20w-50. I run this combination all season and change it very 10k miles....it's mostly highway miles on the 240.

Cheers,
SM
--
90 BMW 325is, 98 BMW 528i, 90 Volvo 240DL

The information I've seen on synthetics indicate they have superior cold flow and heat resistance. At your temperatures you could consider going to a 5-30 weight for easier starts and faster build up of oil pressure. In summer switch to 10-30. Here in Oregon I use 10-30 summer and winter. I use Amsoil but Mobil 1 is good also.

Read the oil information in the FAQs, same engine as the 240.

I live in Canada and use Mobil 1 in my 1988 244. I get it at Canadian Tire or at Walmart. I hear its better . . . who knows? I use it because I change my own oil and since I only do it twice a year, I like to know I'm doing my engine a favour . . . Fred PS. I know synthetic doesn't necessarily mean I can extend my oil change periods, but it's 12 degrees out there right now, and there isn't any way I'm crawling under my car to change oil.