For semi truck engines, the delvac is a bit wimpy (it burns off easily. It seems to be popular in stationary pump and generator and agricultural engines that sit for long periods of time ) , but I imagine in a car it would do very nicely. Diesel oils always have more detergents, and better soot handling chariteristics than straight gas engine oils.

The Chevron Delo is less likely to leak / burn off than the other diesel oils, but does not handle soot quite as well( which shouldn't be a problem in a gas burner ).
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-------Robert, '90 240 wagon, '84 240 diesel , '80 245 diesel

Delvac is good stuff, no doubt about it. Likewise for Shell Rotella-T (which is available in several other viscosities).

The one concern with some of the "diesel" (heavy duty, 15w40) oils is that they might ("might") harm catalyst. That would be only in extreme cases where the engine was consuming large amounts of it.

I've used various brands of 15w40 in my Volvos periodically. We have very hot summers here, and I used to work in thh funeral business, where I'd be idling for long periods, and leading low-speed processions, and sitting still with the A/C on for 1/2 hour, etc. In addition to that, I was also driving a lot of highway miles. For these reasons, I felt that it was definitely not detrimental, but was perhaps beneficial to use this oil. In moderate climates a 10w30 should be fine, as you shouldn't use it in really cold weather; something like under 20 degrees (for most gas engines).

Like Rob, I also saw very (VERY) clean engine internals. That is the case with most of my cars. I think if you use even Castrol GTX, it will stay relatively clean when you stick within a reasonable interval for oil changes. Additionally, if you drive a lot of highway miles, the inside of the engine will almost always be very clean, unless you neglect changes.

--
Chris Herbst, near Chicago.

Go to Ed's oil page formerly known as Bob is the Oil guy find the used oil analysis - Delvac has had some decent analysis...
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www.fidalgo.net/~brook4

FWIW I've been feeding my 86 Sunoco or Castrol 15W-40 exclusively for almost 60,000 miles now, changes every 3000 with a new Mann filter.... my father was over the other day when I changed the valve cover gasket and he saw the inside of the valve cover. He remarked, "that cleaned up real nice." I said, "Dad, I didn't clean it!" The engine is pretty much spotless inside.

Last year I changed the 88's valve cover gasket too and it looked the same at 190K... I've only had that one for 40K miles but I expect the same results.
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Rob Bareiss, New London CT ::: 'Roterande Fläkt Och Drivremmar!'

Any oil that you can buy over the counter will be more than adequate. Shell Rotella is inexpensive and readily available. Use a high quality filter (Volvo or Mann) and change it every 5,000 miles.

Probably very little to be gained from switching to synthetic at 160k.

The viscosity is a little high and will reduce both fuel economy and other benefits such as optimal engine cooling. Better to use a 10-30 or 5W-30, preferably a synthetic. Have you tried Mobil 1?