grygst76

I was running 10W-40 for one oil change and found some interesting observations.
1. Cam surge starting and stopping. it was weird I could feel the car slightly bucking under 1700RPM's
2. Lifter noise. I thought my rockers needed adjusting because it was pretty distinct of loose adjustment, but I have polylocks.
3. lost mileage. I lost 30 miles to the full tank.
4. Sluggish performance. I said it, I felt the car did not want to get up and go like it used to.
5. Rough warmup. When she sat overnight and I started her in the morning she ran like she had a big cam in it, the car would shake until she was warm.

So I switched to synthetic blend 5W-30 and a pf1218 filter. I got my mileage back. I also have very little lifter noise. she starts up smooth and the car does not shake. Granted my pressure is down at idle and cruising but only by maybe 5-9PSI. so my conclusion is the LT1 does not like thick oil. Funny thing is my car has 111,000 miles on it..

Type_O_Negative_1320

Not to hijack your thread, but I'm having similar issues.

This is on a somewhat fresh 383 with about 7K miles. Pressure at idle on startup is 40 PSI...driving around for a few minutes and then whacking the throttle will kick pressure up to around 60 PSI. Once the engine is totally warmed up (after a highway drive), pressure will drop to about 20 PSI at idle and 40 PSI cruising. Pressure will not increase over 40 PSI when warm, no matter how high I rev it (I shift around 6200-6300...runs out of power after that). All of the above is true with either 10W40 or 15W40 oil.

I've also noticed the lost mileage, ticking valvetrain, and rough cold start idle like the previous poster. I'm wondering if I should switch to something thinner...however, I was told that the engine was built with loose tolerances and that I should run the thick stuff. They recommended 15W40 for the winter and 20W50 for the summer.

I'm getting pretty confused...anyone have any ideas or past experience with this stuff?

grygst76

with a heavy oil it seems you should have a higher oil pressure but pay in mind, on my old 327 I ran 20W-50 racing oil and had the same problem as you describe. cold oil makes for higher pressure. I am going to invest in a good quality air-to-oil cooler to keep the temps down for the oil to keep it "thick." Looser tolerances is a strange answer to a pressure question though try running it with 10W-30 for a few hundred miles and see what happens, what could it really hurt?? Just don't spin it to the moon

Type_O_Negative_1320

That may be part of my problem (oil temperature, that is). I've been running Valvoline Durablend in there...maybe I should swap it out for Mobil 1 since it holds up to heat better. I'd run an oil cooler, but I don't have the capability to hook one up anymore (the fitting between the filter and the block where it would hook to was removed during the rebuild...long story).

As far as thicker oil weight for loose tolerances...I was told the oil needed to be thicker to make up for the increased clearances on the crank and rod bearings. I have no clue what the hell they're talking about either...I just do as I'm told.

grygst76

you can still get one, I had the stock oil cooler and took it off because it was water cooled and if my coolant temp was high then the oil would be too!! when you buy the oil cooler kit it comes with all you need to get it hooked up minus any extra zipties you might need. The engine tolerances for the bearings IMO shouldn't be "loose." Try the 10W-30 at first and see what happens.

Patman

I've been trying out a few different oils in my LT1 and doing oil analysis on them to see what works best for me, and most recently I switched to the new German made Castrol Syntec 0w30. Unlike the other Syntec oils, this one is a true synthetic, it's actually rebottled Formula SLX.

This oil is a very thick 30wt oil, at 12.2 cst at 100c it's only 0.3 away from being a 40wt. I've always maintained that the LT1 would like an oil that is a high 30 to low 40wt oil and after seeing my oil analysis results on this new oil, I'm more convinced than ever! My wear numbers on this stuff are simply incredible, most notibly I only got 3.6ppm of lead in my last 3k interval (yes, I ran a very short interval) And given my frequent full throttle driving, and the 9 quarter mile runs I made during that interval (many of which were made with the engine almost stone cold, which is not the best thing to do in terms of longevity!) the numbers I saw were incredible.

This is why I'm not a big fan of Mobil 1 5w30/10w30 in the LT1, it's simply too thin for best wear numbers (they are only 10cst at 100c, almost 20wt oils-since 20wt is 5.6 to 9.3cst)

Other good choices would be Redline or Amsoil 5w30, both of which are also close to 12cst at 100c.

Type_O_Negative_1320

Where do you find these? My local Pep Boys tends to have a pretty crappy oil selection, hence the reason why I'm currently using 10W40 Durablend. I did rummage around for the Syntec after reading your last post about it, but couldn't find it.

grygst76

you have to go to the store and look at the back on the label and look for made in Germany, I always used Castrol GTX and loved it, currently using their 5W-30

Kuma

Amsoil and Redline are most easily purchased online. You can get the Amsoil more cheaply than Mobil 1 if you become a preferred customer, which costs about 30 bucks a year.

Redline is too expensive and not worth it IMHO. $7.50 a quart??

I run Amsoil 5w30 and 10w30. Truth be told, I think the former is better for the LT1, the 10w30 is almost too thick, my valvetrain gets a bit noisier when I put it in. The 5w30 seems about as perfect as you can get.

Patman

I prefer a 5w30 or 0w30 over 10w30 and here's why. When it gets a bit colder out, the 5w30 and 0w30 will flow a lot better, and therefore your cold oil pressure is not as high and this also means your oil filter doesn't go into bypass mode as easily during this time.

During the heat of summer though 10w30 will flow just as well, so it's a non issue then.

I used to hate 5w30 and 0w30 oils because in the past they used to thin out so easily, but the most recent high quality synthetics don't do this anymore. I was especially happy to see the 0w30 Syntec I use did not thin out one bit during my last interval. I sent a new oil sample from the same batch and it tested out at 12.2cst, exactly the same as how it finished up! This is because this oil uses little to no polymers in it to achieve that wide viscosity spread. It uses a very good base oil to acheive it.

When using conventional oil though, 5w30 is not the way to go, as it will thin out very easily. If you use conventional, stick with 10w30, or one of the thinner 10w40s (Pennzoil 10w40 comes to mind, as it is 13.5cst, at the bottom end of the 40wt range)

S.J.S.

Hey Patman.....I thought you told me the 10-30s were to thin for the LT1 motor. You said 10-40 was the way to go in Mobil1 didn't cha?

Patman

If you're using Mobil 1, their 0w40 is definitely the better choice over their 5w30 and 10w30.

As far as me saying 10w30s were too thin, that's not the case. It depends on which brand of 10w30 you're referring to. I think a 10w30 that is formulated at around 10cst at 100c is too thin (such as Mobil 1's 10w30) but a 10w30 formulated closer to 12cst (like Amsoil or Redline) is not too thin at all.

I strongly urge more of you guys to do oil analysis, and see what oils work best for you.

kmook

Gee I've been searching for that german stuff and all i find is the USA stuff.

Is there any spacific place that is more likely to have it? Autozone, Discount Auto, Walmart, Napa???

Patman

The only place it's been spotted at in the US so far has been Autozone.

You might have a hard time finding it in FL, just simply because not many people use 0w30 down there, so Autozones don't order it often and end up with the old stuff gathering dust on their shelves.

Although German Castrol has been spotted in many parts of California and Arizona though.

It was hard to find up here when it first came out, but now it's way more widespread. In Canada it's at Walmart and at many Canadian Tire stores too.

grygst76

Now all restaurants are Taco Bell!!! (Demolition Man)