TOPIC:

Well, the learning curve continues... I have been running a lovely '88 760 Turbo Intercooler wagon up and down I-5 from San Francisco to Seattle regularly now for nearly a year. The all original engine now has 196,000 miles on it and only seems to run better with every 850 mile run. I don't know what oil has been run in this engine until now, but a friend recommended changing the oil I am using from a 5W-30 to a 15W-40 Delo. His thought is that there are better detergents and more zinc in the Delo, which might, even at this late date, add to the engine life of the vehicle.

His thoughts make sense to me, especially since the majority of the miles I put on the car are long runs running high speed through mountain passes. His recommendation was "Delo diesel oil," which kind of widens the field of choice for me.

Does anyone have a more specific recommendation?

Many thanks,

David

Sad that you have no knowledge of the engine oil type that produced all those initial miles and a healthy engine but...

Them what knows the B230FT like a brother agree on how to spell B230FT but differ on the best oil for the street.

Given your journey at mostly highway speeds over varying terrain and in changing climates you may wish to run oil in the 5W-40 range and the Delo for the diesel engine is indeed one candidate.

Yet others prefer full-synthetic or even a blend.

Now comes a Volvo Guru swearing by Rotella 15W-40...

No, wait! Here's a guy with 300k on his B230FT running Mobile 1 for turbo diesels...

"... motorcraft 15w-40 powerstroke diesel formula..."

And the winner is...

tinyurl.com/htp2ucg

Shell Rotella T 15W-40 Heavy Duty Diesel Oil!

George Dill

I am a retired chemical engineer. IMO, 15-40 oil is the wrong viscosity for your tutbo I4 engine. The basic principle is always maintain a mono-molecular film on all of the internal metal surfaces of the engine. This prevents galling of the wearing surfaces. Cold starts, and hard acceleration are the conditions that are the worst for allowing surface galling to occur. In the winter, a 5-20, or 5-30 blended oil is best; summer a 10-30 blended oil. A full synthetic premium oil intended for gasoline engines is preferred. It is important to also use a premium oil filter, Bosch is recommended. Grit in the oil will wear the metal surfaces, so the oil must be as grit-free as possible. Change oil and filter in the range of every 5,000 to 7.500 miles. It is the filter that must be changed at this frequency, the oil itself is good for 10,000 to say 12,000 miles, but if you really are wanting to be conservative, change both as indicated. Diesel engines run at severe conditions, in the range of 30:1 to 35:1 compression ratios, and the fuel itself has lubricating properties. Oils formulated for diesel engines should not be used in gasoline engines IMO.

Hi George and Lou,

Thanks for the replies. I guess I could give a little more info about the Battlestar. I bought this 760 from a marine engineer friend of mine whose mother's friend bought it new from a dealer in 1988. (I am in possession of the original window sticker--$33,000) She sold it to him and he taught his 3 sons how to drive in it. If I have any reservations about the car, it has to do with those three eightballs.

I know that my friend not only regularly changed the oil, but also took remarkably good care of the car. Although I don't have any receipts for all of the work done to the car, I do have daily contact with the man who can answer every question I can think of to ask.

Lou, I understand all that you said regarding mono-molecular film and galling. In that I live on the West Coast, the car is never in an extreme climate, and it's cold starts are not nearly as extreme as they might be. Oddly, we came to the same conclusion regarding filters, and I regularly use a Bosch.

The perceived advantage of the motor oil formulated for diesels is the additives. I am told that the diesel oils are formulated with an eye to the more extreme conditions found in such engines. In that my driving is 80% highway, I figure that those additives might not be a bad idea. Because I can, and I believe it's good policy, I change the oil at every 5,000 miles; roughly every six months.

By the bye, the sweet old car does not burn a drop of oil...

Thanks again

Hello DH,

My point would be that the additives present in diesel engine oil are compatible by design with the the diesel engine and turbo, and the diesel fuel characteristics. Both of which are very different in a gasoline engine. What you do not want is to form deposits in your 740 engine from the additives in diesel engine oil; or risk the performance of the catalytic converter. What you can do is, for example, use Mobil One full synthetic oil, High Mileage, for gasoline engines. I personally use Royal Purple engine oil, Bosch filters in all of my vehicles, including the Volvo 960, change at 6,000 miles. I have a Ford at close to 200,000 miles that loses no oil between changes.

I would not use XX by 40 weight oil. The oil needs to flow properly to all points in the engine and turbo, filming for an adequate boundary layer on the metal surfaces. Back in the day, 40 and 50 weight oils were used in an attempt to stem oil loss through worn valve guide seals and piston rings. Engine lubricants are very much improved today.

I believe it would fine to use 5-30, or 10-30 full synthetic oil for gasoline engines year 'round in your 740, regardless of the mileage. I would not recommend using separate oil additives, which is actually also recommended against in the Volvo 960 Owners Manual. Changing at 5,000 with full synthetic oil and Bosch filter will virtually stop engine wear. Sounds like your 740 engine is still holding it's engine tolerances, excellent!!

More on oil:

Hemmings Motor News has an online store that sells synthetic blend oil for classic/old cars, gasoline engines, that contains zinc and phosphorus compounds. I don't yet have any data on performance or limitaions to use applications. But it may be worth looking into for possible use in your Volvo. The only full synthetic oil with these additives is 15W50, too high for a Volvo. So it's a synthetic blend only in 20 and 30 weghts. I would say these oils are more intended for pushrod engines. I'll do some more research, and post any additional thoughts here.

Lou Gloystein
Elgin, Texas