Question about going thicker

[HACCOFFICER]

Heres the deal, I have bad piston slap when cold till the engine gets to about 150 degrees. I Am currently using 1.5 quarts of 15w50 Mobil 1 and 3 quarts Mobil 1 10w30. I know the manual says 5w30 or 10w30, however this thicker oil has cushioned the piston slap conciderably. My question is do you think it would be safe to go thicker to lesson the slap more, say maybe 2 qts 15w50 and 2.5 qts 10w30? Or should I stick with my current brew? Thanks


1999 Olds Cutlass GLS 3100 V6 (yes intake gaskets were relaced

) 54K Miles

 

[Gary Allan]

Use a progressive method until no more return is realized ..or other factors present themselves to make you stop.

 

[Carguy80]

what about shell conventional oil,was it 10w40 and there was no piston slap,when you were using it??

 

[427Z06]

Maybe some CLAP would help.

http://www.autoblog.com/2005/10/06/clapped-out-cars-get-better-mileage

 

[Curious Kid]

From what little data that's been provided, going thicker does seem to be of some benefit. Synthetic or conventional yet seems to be proven in your case.

 

[HACCOFFICER]

There seems to be no benefit using synthetic over Dino from the piston slap standpoint, however I use synthetics because of their anti wear and other benefits. I just dont feel right without the best in my engine.


2qt of 15w50 and 2.5 of 10w30 should be ok, right, its only slightly thicker than what I am using.

 

[m2200b]

So use shell rotella t syn 5-40.
You found a solution; just use a syn 40.

 

[Carguy80]

what about shell helix ultra 5w40 or 5w30?they use that same oil in ferrari.if its good for ferrari,its surely good to your car

 

[HACCOFFICER]

Just used the viscocity calculator

My Brew is 100.8CST @ 40C, 14.6 @ 100C

The Shell 10w40 is 99.40 CST, 14.21CST

My Brew is almost Identical. If I thicken Mine up slightly, I just may Have it!!!!!

Next Oil Change = 2 Qt 15w50, 2.5 10w30 OR
2.5 Qt 15w50 , 2 qts 10w30
Plan B = Buy 10w40 (since it seems thicker at startup according to the numbers.
What Do you think?

[ January 28, 2006, 04:10 PM: Message edited by: HACCOFFICER ]

 

[HACCOFFICER]

My bad, I didn't due my percentages right, so the vis of my current brew is less than that of the 10w40, so if I thicken the brew, I should have no piston slap as I did with the 10w40, or even simpler, just buy 10w40 I guess

 

[wileyE]

if your convinced that thicker at startup is better, than why not try a straight 30w?

not sure I agree that synthetic=better antiwear but thats a different subject

 

[HACCOFFICER]

I noticed the shell conventional oil 10w40 had no slap. Its was warmer then, but still there normally would have been some. I just used the shell for a bout 20 minutes to flush out the engine after a gasket job. I would use it again, however I just dont feel right unless I have the anti-wear capabilities of a synthetic floating around in my engine. I just wouldn't feel right with conventional. I guess I have to find the next best thing. I am the kind of person that has to have the best of everything in my car or it drives me nuts.


As you may have read my posts, I have spent over 200 bucks in the past 2 months with countless oil changes and different oils to find a solution, so far I have

-Mobil 1 5w30 - Piston slap loud
-Amsoil 5w30 - Piston slap Loud
-Amsoil 10w30 - Piston slap very loud, other knocking present
-Castrol GTX Startup conventional 10w30 - Quieter than all above
-Castrol Syntec 1.5 qt 20w50, 3 qt 10w30 - Much quieter, engine smoother during slap period
-Current - Mobil 1, 1.5 qt 15w50, 3 qt 10w30 - Same as Syntec, better gas mileage.

I found that going thicker seems to be the key. Now I need to know how much thicker I can go without damage or problems. Need advice on that.

 

[Carguy80]

i think you would be fine using dino shell 10w40 and change it after 3000miles.but if you want to use synthetic how about shell synthetic blend or fullysynthetic?only thing that i have nodest that shell helix oils in sweden dosnt have sae in it (society of automotive engineers)but i dont know if that really is big thing at longest it has api.do you have sae in shell oils in there?

 

[GoldenRod]

I vote for Castrol GTX 10W-40. If that don't work go with GTX straight 30. No sense in buying full synthetic when the motor is beating itself to death anyway. Just my 2 cents.

 

[Oldmoparguy1]

As long as you are willing to spend money, try a 5w40. I use RTS in my turbo Dodge Caravan, (198K miles). Engine loves it, turbo spools instantly. quieted startup lifter tick and piston slap which is common to these engines with high mileage.

 

[Carguy80]

i have tried twice ac delco conventional oil 15w40 in my pontiac firebird 92 v6.i wouldnt put thicker oils that 15w40 in your car.but that just me.watch out that your oil pressure is not going to be too high when you try thicker oils.when i were driving with 15w40 my oil pressure was ok.and car was doing fine.but i nodest that my valve lifters started to knock,so now i have 5w30 oil and it is much quieter.what kind of oil your owner manual tells you to use?

 

[HACCOFFICER]

5w30 is what the manual says, or 10w30, the slap is loud as **** with these two viscosities. It is quieter with the thicker oils.It was gone with 10w40

 

[Carguy80]

have you tried redline oil,10w40?

 

[hominid7]

It's the synthetic....It's apparently too thin at start up for your specific application (as evidenced by your castrol start-up 10w30 being quietest). Try regular old conventional 10w30. Exxon superflo might be a good (and inexpensive) place to start.

Despite what some others may say, Valvoline All Climate is another good choice. It was the only thing that kept my old VW Jetta quiet at start-up. I drove it for 225,000 miles and it never burned a drop. However superflo is a lot cheaper and from my unscientific experience seems to be very decent. I had 10w30 superlfo in my Mazda V6 when it was down around 12*F and it cranked up easily without any hesitation or complaints.

If you must use a synthetic, try motorcraft 10w30 semi-synthetic.

As for the mixing debate, I've never been comfortable mixing oils, even oils of the same brand. Then again, i use a colgate brand toothbrush with my colgate toothpaste, cause it makes me feel better