View Full Version : knocking wrong oil?

08-06-2007, 02:30 AM
hey guys yep i changed the oil. iv been using mobil 1 sen. 10w30 for the 8K miles since motor was rebuild but this oil change came and i couldnt find my oil anywhere. everybody was sold out. my friend had 6 quarts of 10w40 royle purple laying around. i wanted to put 10w40 for the summer anyway so it seemed perfect so i put it in and now it sounds like its knocking when its cold but once it starts to warm up it goes away i think the oil is to thick and once the engine is up to temp. is thins out could this be the chase???
because i have this horrible fear with the bottom ends in these cars :confused:and i dont want to take any chances

Kit Sullivan
08-06-2007, 07:06 AM
The 10W-40 will not cause any problems, but it is not the best oil to use.

Your logic of using a heavier oil for summertime use is a common misconception about motor oil: You want to use the lightest oil you can get away with that will still give you the protection you need. Mobil 1 has all the additive protection you need, and then some.
Heavier oil is harder for the engine to move around, so you get a hotter-running engine, higher emissions, reduced fuel economy, less power to the wheels...none of the things we want.

Stick to a good-quality 5W-30 or 10W-30 and you will be fine. Even a non-synthetic name brand oil is good...specific brands are near meaningless as far as performance differences. They are all very good.

08-06-2007, 05:11 PM
i switched from q peak performance, to motorcraft sythetic blend, 10w30.. never ran better. :D

08-06-2007, 08:19 PM
awesome thanks for the help

Colo Bird
08-06-2007, 10:06 PM
Check the owner's manual, if you have it. My recollection is that it recommends 5w30 unless the ambient temperature can regularly reach over 90F in which case they recommend a 10w30. Also, you might try the 10w30 over the 5w30 if your car has high mileage and is consuming oil to see if it cuts down on consumption. I'm using 10w30 for the first time in my 89 SC with 94,000 miles to cut down on consumption. Also installed an oil separator in my PCV line to see if that's where the oil is going.

08-07-2007, 12:49 PM
In all the following comments, I defer to Kit, since he actually worked in the oil field and I am just a hobbyist.

You may have some valvetrain noise until the engine warms up. I often do in really cold weather. The oil you are using may be a little thick since you just rebuilt the engine. But synthetics have better low temp. flow properties than conventionals, so maybe that is why you had noise once you switched.

09-20-2007, 09:31 PM
Interesting discussion. I just changed my oil from Mobil1 10w30 to a synthetic 5W50 oil and now my car has a knocking sound at idle. It goes away once it revs.

With the M1 10w30, I would get about 65psi at around 1000 RPM's when hot on those real scorcher days, but at 600 rpm idle it would be down to around 20 in gear., but once through about 750rpms it was passing through 45psi.

With the 5W50, she sits at 70psi even at idle unless extremely hot and it would be down to about 45psi, but I'm getting that knocking at idle which is making me very nervous.

Any ideas?

09-20-2007, 10:22 PM
well, its 5w-50, so isnt it a thicker weight than 10w-30. switch back to the M1 10w-30, i bet the chatter will go away.

Colo Bird
09-20-2007, 11:18 PM
My recommendation: Switch back to the 10w30 and adjust your idle speed to 700 rpm if you're worried about the oil pressure during idle. I would never use a multi-weight with such a wide range of viscosity due to all of the additives that are in it.

09-21-2007, 08:54 AM
I've gone to heavier weights before and get the same noises etc :cool: but folks keep saying run the heavier oil or else. The motor's bottom end is still original at approx 120k miles on it.

The 5w50 full synthetic oil is supposedly the oil used in the Ford GT supercar and Shelby GT-500 by Ford..... oh well.

I'm getting the M1 10w30 and by god I'm sticking to it.

09-21-2007, 06:27 PM
Went back to the M1 10W30 and all is quiet and peaceful again :D....

09-21-2007, 07:55 PM
thats good.

i've got 144k on the original engine. i use motorcraft 10w-30 synthetic blend. i dont believe that if i dont run a thicker oil, bad things will happen.

09-21-2007, 08:42 PM
If I remember there was a TSB out for the 4.6 engines that were developing a "Noise" while running 10-40. It was determined that the oil was to thick and causing the oil to not drain back to the pan fast enough to be picked up. SOmething about the oil passages being to small to promote a fast return. If I can find the link, i'll post it. Also, go to here and look at the folks here. May shed some light on the subject.