I am about to make a 2500 mile trip from Philly to S. Florida and back. The car is a non-turbo SAAB 900S with a 2.3l DOHC 16V engine with timing/balance shaft chains. These engines are known to have oil related problems when non-synthetic oil is used for extended intervals. Many have failed recently with worn chain guides/sprokets and clogged oil pickup screens.
I have been using a fully synthetic PAO-base German-made Lubro Moly 5W-40 oil. I have done analysis (see UOA section) and have confidence that this oil can go the distance. I always change at around 10k miles, per owner's manual.
I currently have 8200 miles on this interval. I am getting cold feet about leaving the Lubro Moly in there for the trip and 2 weeks (+600 miles) after the trip until I can change it. Doing so will mean making a high speed long highway run (often 100+ mph) using oil that is on its last leg. My usual commute is about 50% city, so there is some stop and go in the 8200 miles that I have already put on this oil. So you can see why I am hesitant to leave it in there for no good reason other than principle.
So now I have to make a choice as to what to use. I have plenty of Lubro Moly 0W-40, which I am going to use in the car year around. I could just use that. This oil is ACEA A3 rated, so we are talking high TBN and HTHS numbers. However, I am concerned about the high heat of this drive and have second thoughts about using a zero weight oil. I also read some pretty strong comments about not using 0W- and 5W- oils in SAAB engines. The comments are made by SAAB service techs who claim to have seen problems using the thinner oils. They recommend Mobil 1 15W-50 for hot weather and a mixture of 10W-30 and 15W-50 for winter. So I bite and buy a jug of Mobil 1 15W-50 at WalMart. However, I reread my manual and it says:
API SH rated oil. 10W-30/10W-40/5W-30/5W-40 or 15W-40 in summer. No preference as to what weight.
So now I am thinking that maybe I should not use the 15W-50. I am more concerned about the commuting after the trip then any wear during the trip. The 5.11 HTHS number is nice, though. I could just drain it right after the trip but that goes against my synthetic oil principles
Looking at the specs of different oils, I have come up with two more choices. Mobil Delvac 1300 Super 15W-40 and Castrol GTX HM 10W-40. The Mobil has the recommended viscosity and a nice HTHS of 4.3. I don't have the HTHS number for Castrol but it's viscosity at 100'C is similar to Mobil's, so maybe the HTHS number is not bad.
After thinking it through, I have decided to use Delvac 1300 Super 15W-40. It seems to be the best combination of low cost, good additive package, good comments on this site
and a high HTHS number for long high speed drive in hot summer temps. And I will drain it after putting 3100+ miles on it.
So, the choices are:
1. Leave LM 5W-40 in and drain at about 11300 miles.
2. Use Lubro Moly 0W-40, ACEA A3 rated (HTHS 3.5+)
3. Use Mobil 1 15W-50 for the trip and perhaps leave in for a total of 5000 miles. 5.11 HTHS but not recommended in owner's manual.
4. Use Castrol GTX HM 10W-40 and drain after 3100 miles. Nice viscosity numbers.
5. Use Mobil Delvac 1300 Super for low cost, high HTHS specifically for this trip and drain after 3100 miles.
What would you choose?!