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Discussion Starter · #1 ·
I am running gtx 30wt in my 81 motor right now, my 71 motor was reading real real low oil pressure, the junk yard 81 motor was just a hair under half seems to be less now, warm weather? I am about due for a oil change, is the vicosity breaking down? or am I just paranoid about every **** little squek , noise, hic up the car makes.
what weight do you all recomend for warm weather driving 80-90 degrees
 

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Discussion Starter · #2 ·
The atmospheric temperature doesn't make all that much difference unless the engine is allowed to overheat. In order for oil to lubricate a Z engine properly, it has to be circulating at a temperature above 180 degrees, that's why there's a thermostat that allows the engine to reach its operating temperature before the radiator fluid begins cooling it. Run 40 weight oil in your '81 engine, it will lubricate the parts more efficiently and your rings, seals and crankshaft will last longer.
 

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Discussion Starter · #3 ·
<b>RE: oil weight question and opinions needed</b>

i started using mobil 1 15w-50 recently. the biggest difference is in the valvetrain. the clacking of the cam followers is greatly subdued.

-casper
 

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Discussion Starter · #4 ·
<b>RE: oil weight question and opinions needed</b>

I'm Using 20W50 syntec blend......economical and good.
My oil pressure sticks between 50 and 60 psi on highway driving 2500-3000rmp on my 83zx w/165000 miles.
Mobil 1 is great for sub-zero temps , I use 0W30 now.
When I used 15W50 I had a lot of oil pressure play...between 35-55psi while driving with 3000rpm
 

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Discussion Starter · #5 ·
<b>RE: oil weight question and opinions needed</b>

Im also using mobil 1 15w-50 and it is working great. I drive the living sh$& out of my car and nothing has broke in the engine yet.
 

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Discussion Starter · #6 ·
One Slight Problem with 50 Weight Oil

It causes your engine to run slightly harder by increasing strain on the crankshaft, valves and valve springs slightly, because it doesn't break down as it should at an L28 engine's normal operating temperature.

Of course valve clatter is lessened, because the valves are moving more sluggishly under marginally increased oil pressure and the cushion of lubricant in the valve seals is denser. The car is speeding toward an engine rebuild but the driver figures everything's okay because the engine is quieter.

When you use engine oil that's too heavy nothing seems to be going wrong till you bust your crankshaft or get tapped for new valves and piston rings, then the difference shows up in the size of your bank account.

One of my goodbuddies once told me to go to heavier oil in a Harley I had. The first time I ran the thing hard, it made the 74 engine into a handsome piece of wrought iron bric-a-brac; and Harley mills are a **** of a lot tougher than Z-Car engines.
 

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Read Z Owners Manual

There is a page in the owners manual that has oil weight recommendations based on ambient temperatures. In most environments a 10W-30 or 10W-40 will work year round. Castrol GTX is a good choice. Change it and the filter every 3-5,000 miles and your engine will last next to forever. THe synthetics will hold up to extreme abuse seen in all out racing better than a standard oil but the standard is more than adequate for street driving and a lot cheaper. If you want to spend more money on oil, buy the standard, and change it more frequently. The filter will remove particular contaminants but it won't remove combustion byproduct acids that will eat at your bearing surfaces when the engine is resting - which is more than when it is running.
You could also invest in a "pre-oiler" It's an electric pump that comes on before the car starts and brings oil pressure up before the engine starts. That way the engine never runs "oil dry".
Phantom
 

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Discussion Starter · #8 ·
RE: Read Z Owners Manual

Phantom makes an excellent point. Changing your oil more often is some of the best and cheapest engine insurance you can get. At less than $10 per oil and filter change every 2-3000 miles, it's virtually nothing cost-wise with standard oil. Synthetics may seem cool for street cars, and do make a big difference in cold weather, but often the extra money would be better spent on new clean oil and a new filter. The only time they react like the Mobil 1 ads show, is when you overheat your engine. Don't take the advice some give about synthetics letting you go 25,000 miles unless you change your filter and top off the oil. You may just clog your filter and end up bypassing it (most cars have this feature built in). It saves the engine from oil starvation, but usually doesn't tell you it's doing it. Then you run without a filter, and that can be very costly.
 
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