Does anyone have any thoughts on using straight 30-weight synthetic oil on a '97 with 102,000 moles?
The motor runs well, and uses no oil. It's just a little noisy.

Sounds like a Star Trek movie...

I think you are unnecessarily increasing start-up wear while sacrificing fuel economy before the oil reaches operating temperature by using a straight 30 weight. If it's a racing oil, then it is not a good choice for a street-driven car.

What specific oil do you have in mind, what type of driving do you do, and where do you live?

It seems that the effect on start-up wear and fuel economy should be negligible. As I recall from researching Amsoil, Neo, and Redline specifications a long time ago, the flow numbers, shear numbers, and friction numbers of high-end synthetics manufacturers' straight 30 appear very close to the multi-viscosity oils like 10w-40 and 5w-40.

I agree with you on the racing oil, as the trade off of less detergent to get less friction also results in more sludge. I can testify that you do not want to rebuild one of these engines.

Enlighten us MITOG. ;-)

P.S. Engine Rebuilt update: No photos recently, but the bottom end is done (3-way plastigauged on each crank and rod bearing, all clearances triple measured, and crank turns without any hard spots), oil pan also put together, now migrating to various block components/seals before starting the heads.

Did you check all the spark plugs make sure there snug? Also is it lifter tick or what? The 12v is a little noisy shouldnt be to loud with the hood closed though. Heavyier oil will only cover the noise for a little longer. Probably end up with bad gaskets/seals better to fix when needed then cover up and fix more a little down the road.

Enlighten us MITOG. ;-)
<b>I'll gladly pass on some facts, which may or may not be tainted by false information, misinterpretation, and my personal agenda. I HOPE my opinions are mostly based on fact rather than on fiction and belief. ;-)</b>

It seems that the effect on start-up wear and fuel economy should be negligible.
<b>Wear during the warm-up phase is on the order of a few hundred times compared to under operating temperature. Having gone from 5W-40 to 15W-40, I notice a huge drop in fuel economy. Comparing the cSt viscosities, the reason is obvious: of those two oils, the 15W-40 is the thicker oil, which is harder to pump when cold. Keep in mind it's not really cold here in SF.</b>

As I recall from researching Amsoil, Neo, and Redline specifications a long time ago, the flow numbers, shear numbers, and friction numbers of high-end synthetics manufacturers' straight 30 appear very close to the multi-viscosity oils like 10w-40 and 5w-40.
<b>I don't know what oil hegira was considering. That's why I asked him to be specific. Analyzing the spec sheet for an oil will allow to make a specific statement. Generally speaking, a 30W oil will be thicker when cold than, for example, a 5W-30 or 10W-30 oil. In the case of a high-end oil the numbers may be in favor of the straight weight oil. That's the case for example when comparing Rl 30W and RL 5W-40. Red Line 30W Racing oil would pass as a 10W-30, and the data sheet even states that clearly.

Pour Point (I guss that's what you mean by "flow numbers") means little, as it does not equal pumpability. The oil may flow, but your engine might not be able to crank.

Shear numbers? I guess you mean HTHS (high temp/high shear)?
HTHS of Red Line 30W is nowhere to be found, but most likely a little under 3.5:

HTHS of Red Line 5W-30 is 3.8
HTHS of Red Line 10W-30 is 3.8
HTHS of Red Line 5W-40 is 4.6

If you mean shear stability, then it's easy to compare different oils by calculating the ratio of kinematic viscosity @ 100C, to the high temp/high shear viscosity @ 150C. The lower this ratio, the more shear-stable the oil is. The viscosity units are mixed, centistokes and centipoise, but you want to look only at the numerical result. </b>

I agree with you on the racing oil, as the trade off of less detergent to get less friction also results in more sludge. I can testify that you do not want to rebuild one of these engines.
<b>Many racing oils not not contain ANY detergents. Racing oils will often oxidize rapidly, which requires the oil to be changed often.</b>

P.S. Engine Rebuilt update: No photos recently, but the bottom end is done (3-way plastigauged on each crank and rod bearing, all clearances triple measured, and crank turns without any hard spots), oil pan also put together, now migrating to various block components/seals before starting the heads.
<b>I wish I could be there the day you fire her up for the first time! Please keep us updated.</b>

102,000 x 6.02x10^23.

thats a lot.

My next question would be to ask for recomendations of brand. I live just south of Boston, and drive mostly short hops, with the occasional blast to the Cape (of Cod).
Thanks, Oh Great and All-knowing Mori....

What oil have you been using and what are you currently using? What's noisy and when is it noisy?

not my crowd. Not that there's anything wrong with that.....
I used Valvoline 5w-30 in winter, 10w-40 in summer up until 75,000 mules, when I did the timing-belt, then switched over to M1 0w-30, 5w-40.
The noise sounds like lifter noise, but as has been said, maybe that's the nature of the beast.

I used to live in Boston and went often to the Cape. I know what's down there. :-P


If the lifters are only noisy for a short while after a cold start, it's not an issue. If lifter noise occurs on other occasions, the oil's viscosity may be the cause, or maybe the oil retention valves are faulty.

Given the cold Mass winters, I think 0W-40 might work well for you during the cold season. During the warmer time of year I'd suggest a 5W-40.