I religiously change oil every 6 months or 5,000 miles. In my W115 I go 6 months for 3,000 miles because of the age of and mileage of the car.

Anyway, I generally don't hit 3,000 miles in a 6 month time frame, so it comes down to time being the limiting factor.

I'm not sure what sort of oil the PO used, but I swapped it out for Rotella T6 5W 40. As time passed I started to develop leaks at the front and rear seals. Also, oil consumption increased. I understand there's a lot of urban myths about synthetic vs dyno. I don't want to go there. Besides, I'm not going to say that it was the oil's fault. The PO rarely drove the car whereas I'm averaging 5,000k/year. Those nagging issues were probably waiting for a serious driver to come along before their reared their ugly heads.

Anyway, I noticed that Delvac 15w40 is half the price of Rotella T6 today. Since I'm not going to see the full, long life benefits of synthetic, I'm thinking about switching to the Delvac.

Any thoughts or concerns?

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1974 240D "Boldie" 170K.- New timing chain/freshly rebuilt IP/replaced valve seals/injectors/upgraded stereo/new Bilsteins with Yokohamas/fresh paint and rocker panels plus lots of welds.