Oil Change Question

[SofaKingFast]

I'm not really an expert on cars so sorry if i ask a dumb question. I changed the oil on mo '89 MGM, with Castrol Syntec 20W-50 and 1 quart of lucas. She doesn't run any different now but sometimes the engine makes kind of a diesel grumbling sound sometimes especially when idling. It doesn't sound like a knock or ping, I'd just like to know what this is and if its bad.

-Thanks

[BerniniCaCO3]

I don't know about the sound, but isn't 20w-50 kindof thick? I've always used 10w-30, even 5w-30 in the winter, without issue.

When your engine is idling, the power output is much lower than when you're at any sort of cruising speed. The oil pump is turning much slower.
The particular consequence of too THIN an oil would be low oil pressure at idle. I don't know about too thick.

Is it every time it idles, or, just on cold startup?

When you first start an engine and the oil has not of course warmed up, it's much thicker-- and very much thicker if it's 20w-50. It's possible that the upper valve train isn't getting enough oil, until you get on the road and the oil both warms up, and the oil pump is turning faster because you're cruising, moving more volume.

[SofaKingFast]

Usually it does it every time it idles. I changed the oil from 10W-30 conventional to 20W-50 synthetic thinking that 20W-50 would be better for the warm weather here, especially in the summer. Next time I change the oil I think I'll go back to 10W-30. What do you think?

[351m]

What is wrong with the engine that made you decide to dump the Lucas in? As far as the 20W50 oil, it shouldn't cause any problems in the summer, its not needed but shouldn't hurt anything. Did the noise show up after the oil change or was it there before?

[SofaKingFast]

Yeah the noise showed up after the oil change. There's nothing wrong in the engine, I just thought that Lucas oil would be good to use every once in a while.

[GM_Guy]

You should never really have to dump anything into your oil, especially if there is nothing wrong to begin with.
This lucas stuff a thickener? You've possibly got a syrupy oil now. Keep in mind, the thicker the oil, the harder it is to pump the ticking you hear is the pump struggling to pump the oil.
If I where in your shoes, I'd drain what you have now, and run at most a 15w40 if you find you've got oil consumption problems. If to this point your car has not used oil using 10w30, I'd stick to using it. When you find you need to add oil for no apparant reason you can pop to the 15w40 and start saving up for an eventual rebuild (note: eventual, not immediate or near future) If your engine is worn to the point that its drinking 15w40, then you can give 20w50 a go becuase theres enough slop and clearance everywhere that 20w50 will flow semi-easily.

Alex.

[marquisman]

there is nothing wrong with 20W40 in the summer. we use 25W40 in boat engines. only possible difference in sme engines would be the oil pump. i run 15w40 with a spash of lucas oil stabilizer in the summer and 10W30 in the winter. people have a misconception about lucas. and synthetics are over rated. the lucas oil stabilizer helps prevent oil break down and promotes viscosity. only thing is, using one quart is much. i use half of that, if that

[gadget73]

I use just oil in all of my motors. Never seen the point of dumping magic potions in them. None of my stuff makes goofy noises either, and for the most part I have not been brand loyal. I do tend to stick with the mfg's reccomended grade of oil though. For my Fords thats 10w30 or 10w40 all year long, and 5w30 in my Chevy.

[SofaKingFast]

Hmm. Ok thanks everybody. I think I'll wait until I need an oil change again and I'll put in 10W-30 like it had before but I'll put half a quart of Lucas in this time. How big of a difference does synthetic oil make rather than conventional oil?

[marquisman]

its a matter of life an death

[SofaKingFast]

Really? I thought that synthetic lasted longer.

[1990LTD]

Really? I thought that synthetic lasted longer.

He was kidding. I think.


The argument made against synthetic oils in an older engine (high km or no) is that the detergents in the synthetic oils will clean out the crankcase - including any deposits from old oil (remember that time you went a few kms over your oil change interval?) that may be plugging leaks, however small, in gaskets and seals.

They're generally advised against in an older vehicle, or any vehicle with questionable maintenance history

[SofaKingFast]

Well ok. The oil in my car was always changed regulary. The previous owner worked at an oil change place and gave me a bunch of maintenance records to prove it.

[gadget73]

my Mark 7 has 235k miles on it. It was changed every 3k miles, and at 180k it was switched to synthetic oil. It doesn't burn any oil, and other than the valve cover gaskets being slightly leaky when I got it, it did not leak. New VC gaskets and it even quit leaking. I've had the valve covers and the timing cover off that motor, and it looks like new inside. The oil pump is shiny down there in the pan, and the inside of the motor doesn't even have that dark brown baked-on varnish looking crap that most motors have. I switched my S10 to synthetic at 150k, and its fine 4000 miles later. No leaking or burning. I wouldn't try it with something that wasn't regularly serviced but if the motor isn't nasty and sludged up now, you should be OK with a synthetic oil.

[SofaKingFast]

Ok, thanks for the advice.