Best oil in a straight 8?

[Guest 1950SuperPDX]

Was wondering what you all use in your straight 8's? I did an oil change and now i've got a lifter clicking the valve cover when she's cold, and it actually really never goes away, just gets quieter. Before the oil change it was just fine..

I used Valvoline VR1 20w-50 with high zinc.

[Larry J]

I'd be interested to hear what others have to say on this. I have a 38 Olds straight 8 that is being rebuilt as I type this. The shop manual says to use 20-W or SAE 20 for temperatures not lower than 32 degrees F and to use 20-W for temps down to plus 10 degrees F. Then it says to use SAE 30 in the summer when average daylight temps are 90 degrees or above.

[The Old Guy]

I used to run Valvoline 10-40 ,but now I run Shell Rotella 15-40 They have reduced the antiscuffing additive (ZDDP) in many oils but this still keeps them alive. My 40 has been over 107,000 miles with me and is still running strong

[NTX5467]

The "20W" section of the oil spec is for 0 degrees F oil temperature. Any oil temp higher than "zero" would mean it would be thicker. Even with the possibly looser internal clearances, the "50" part of the spec might be too much. Some of the later VR-1 oil analysis reports I've seen (Welcome) indicated that it is not quite so high in zddp as some might suspect OR might have been in prior times.

What you might also have is an air bubble from the oil galley that went into a particular lifter, which the thicker oil might not be letting "out".

When I installed an engine I had built for my '77 Camaro, we did the break-in miles on Valv 30, then I put my prior Castrol GTX 20W-50 in it. I noticed an immediate decrease in throttle response from the 30-weight oil, due to the 20W-50 (which I ran in the production 305 for 500K+ miles with no problems or anything), so I went to 10W-40 and the throttle response came back. It just takes more power to run the oil pump with that thicker oil in the system!

When you stop the engine, the oil in the oil galleys will return to the oil pan. Upon startup, the air has to go somewhere (even if it's out around something or through a designated bleed hole). In the earlier Chevy big blocks, some of them would get noisey valve lifters just after an oil change. The "fix", per TSB, was to drill a .020" hole in each of the core plugs for the lifter oil galleys, on the front end of the motor--later, the holes were incorporated into normal production parts. You can imagine the "concerned customers" whose engines suddenly had lifter noise after an oil change, when no lifter noise was there before.

I'd see if it might go away with use, but if it does not, then replacing it with the Rotella T "dino" or 5W-40 synthetic . . . or a 10W-40 oil of current availability (IF you read the back of the oil bottles, there are many available 10W-40 oils which are "SL" oils rather than the "SM" and "GF-4" ratings) might be an option.

Just some thoughts,

NTX5467

[Guest Charlie Larkin]

Lately, most of my hanging around car-wise has been with Hudson people, and in their cars, almost all of them swear by Castrol GTX 10-30 or 10-40. A couple with slightly built 308 L-head 6s use GTX 20-50 for a little extra lubrication. A couple of real old timers still use Amalie (I can't even find it!) or Kendall, which I've tried in my newer cars, and it seems to be good oil.

A few have used Rotella or Mobil Delvac with good results. Almost universally, they add at least a pint of Marvel Mystery Oil for better lifter lubrication, which seems to have have helped cure the zinc (non?) problem. A good number, though, just pour the full quart in.

My friends with Packards and Nashes seem to like any good 10-30 with a quart of Marvel.

Sometimes, you can learn from people with other makes. As my one toy (1966 Skylark) is out-of-commission, and I have a love of cars in general, I try to pick up as much information as I can from as many different people as I can.

Charlie Larkin

[Airy Cat]

I run 10W 30 in all of my Buicks and have had no problems with it.

[mrspeedyt]

walmart has 'accel' sae 10w-40 'SF' oil for $2.40. gonna try a quart when needed. note: 'accel' doesn't look like the hi-po ignition brand.

[Guest Straight eight]

I stand to be corrected, but, I always thought that 10W50 does NOT get thicker, it stays a 10 weight as far as pour ability, but has the lubricating qualities of of 50 weight.

[NTX5467]

The "10W" flow spec is for 0 degrees F. The higher number is at normal operating temperature. Hence, it starts out flowing easier when cold, then gets thicker as the engine temperature rises. Saves strain on the starter and such in cold weather, being easier to turn over than it would be if it was a straight-weight 50 oil.

Enjoy!

NTX5467

[Guest presten]

I think some of you should go back to school regarding oil viscosity information. First there is no automotive oil made the "gets thicker as it gets hot" That is completly incorrect. All oils get thinner as they got hot...the amount of thinning or percent of change with increasing temperature is known as the "viscosity Index" An oil with a perfect viscosity index would stay at the same viscosity regardless of temperature. Such an oil would have a flat Viscosity/Temperature curve (if one existed). Now the oils with designations such as 5W-30, 20W-50, etc are known in the trade as "Multiviscosity oils" They have additives in them that reduce the thinning with heat..note it reduces, not eliminates thinning. Therefore a 5W-30 oil will have the same viscosity as a standard 5W oil at low temperature but still retain the viscosity of a 30W oil at elevated temperature. In effect such oils "flatten" out the temperature/viscosity curve to give you some of the benefits of each oil they replace. Therefore our sample 5W-30 oil would be as thin as a standard 5W oil at low temperature but at high operating temperature it would still maintain the viscosity of a standard 30W oil.