auto_editor

Someone recommended using "diesel" oil [15W40] in my long-suffering 307 rather than "normal" oil of a similar [20W50] rating as her low oil pressure light comes on once she's been "hot" for awhile.

The 5W30 works great in winter, but hot weather + long-distance driving resulted in her "oil" warning light first flickering, then staying on once you come to a stop.

A higher-temp oil is necessary, but I've never thought about using diesel oil vs. the standard kind.

SO, if you know about using diesel oil vs. the regular stuff let me know.

Thanks!

AZ455

I use Shell Rotella T 15w-40 in both the Olds and my Toyota. More anti-wear additives (1200ppm ZDDP in Rotella) better soot absorption, better detergents. Been using it in the Toyota for years and in the Olds since I got it.

Lady72nRob71

do a search on oil, diesel, zddp and you will get a LOT of opinions.
I do run diesel oil in my old cars, 15w40 here in hot TX.

MDchanic

I believe that diesel oil is not recommended for your car because it has a catalytic converter, and the higher levels of certain metallic compounds in the oil (including ZDDP) can poison the cat. over time. That's why there are now separate oils for diesel and non-diesel, and off-road and on-road.

- Eric

Funkwagon455

I run Amsoil synthetic in my V8's with the exception of my wife's 360 Grand Wagoneer, it gets Rotella. My oil analysis' have come back very good for three years in TX heat, and with my lovely wife's less than gentle right foot tendencies.

rustyroger

It's the weight of the oil rather than its suitability for diesel/gas that keeps your oil light out.
All else being equal a heavier oil (higher viscosity numbers) will run at higher pressure than a lighter one.
Don't forget when the oil reaches a certain pressure the relief valve will open anyway, and thinner oils get round the engine quicker on startup.
If your light is flickering at idling speed it is indicating the lubrication system is worn, your 307 should have 20psi idling when warm and 40 psi when cruising. Much less than 10 psi idling hot means not long before the bottom end will need attention, check out what pressures you are running with an accurate gauge and decide what you want to do.

Stop Press; I seem to remember you running a thread about swapping out your 307 for another motor a while ago, if you have something lined up but not quite ready yet by careful driving you can run an engine with crummy oil pressure for some time, I've managed it several times in my impoverished past.

Roger.

Lee_A

You could also just have a bad pressure sending unit, or even a bad connection at the sending unit.

Zinc is mainly needed for flat-tappet cams. I believe your 307 should have a hydraulic roller, so zinc in the oil will not really do anything.

As Roger said, it is simply the weight of the oil that will effect your pressure, not the additives. 20W-50, maybe even straight 40 weight. Most likely, though, you have a bearing(s) going away, and the end is nigh.

Lee

auto_editor

Thanks for the opinions. I went with the diesel oil and sure enough the oil warning light issue disappeared, though another one might have started.

It feels as though the rolling-off-after-idling is more sluggish, though it might just be I'm hypersensitive to it now. I doubt the diesel oil can "slow" the engine down, but there's a one-two beat when you step on the gas after sitting (at a light, stop sign, whatever) that I don't remember being there before.

Some said that the hesitation might be an issue with the transmission's torque converter switch/sensor/whatever while others say the timing-related parts--which are plastic?!?--could cause similar stumbling.

All in all though, I have to admire the 307 (or this one in particular) for staying in the game so to speak. I don't know what in the bottom end that's going south--"thunk-thunk-thunk" reciprocating sound with coordinated rocking motion--but so far, so good...

Fastbrianman

I worked for my local county police garage in the early 1990's. We had 900+ cars to maintain. Mostly Crown-Vic cop cars and ran Shell Rotella 15-40 in everything. We never had an engine failure on anything. (Most cars were sold by 150,000 miles) I have run it in my oldsmobiles ever since.