rotella 15-40 in an H

I'd keep using Rotella and replace that front seal.

And FWIW I use Rotella 15W40 in all my old tractors as well as my F250 diesel...

I worked with a guy that had previously been a partner in a deisel repair shop that repaired alot of construction machinery as well. They used alot of Caterpillar oil in Caterpillar machinery to meet specs and warranty issues. His partner was convinced it was great oil and began using in it the shop service truck. In no time at all his truck which previously needed a quart every 2,500 miles began hemoraging oil like the Exxon Valdeez and he had to put in a quart every 600 miles. It was quite evident that the oil was coming out of every seal and gasket. The detergents just did too good a job for that old work truck. He ceased using it and eventually the oil he needed to add grew somewhat less. 1,000 miles between adding a quart at the time of telling the story but it never did get to the point where it had been.

Again, I don't know if Rotella is such a heavy detergent oil. I'd look into the specs and claims. But don't let people who don't know any better try and tell you that there are not oils that will make your engine leak.

Stick with a good diesel-rated oil. Rotella is an excellent choice.

Front seal is only a 1/2 day job, just replace it.

I was using Esso at the time thus went with their series 3 oil, same specs as Rotella. Initially I used 30W in summer and 20 for winter. This included every thing from a 455 Olds, Chevy pickups, skid loaders, gas Farmalls, diesel Farmalls and a 4 cycle lawn mower. Over the years since I've had exceptional results. I switched to 15W-40 about 10 years later. The lawn mower was around until last year, never had a diesel tractor need a rebuild under 10,000 hours, gas 4,000 hours.

When I first switched my Esso dealer told me this oil was only needed for severe service diesels like heavy construction equipment. I said,"I know what you mean, a bulldozer spends half it's day backing with no load, even pushing they seldon use full rated hp, while my 656 and 560 often spend all day under full load, at rated hp." Put it this way, I feel good oil has saved my big money over the years, but regularly scheduled oil and filter changes are just as important.