[NA]Car engine oil

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
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Dave Taylor
I have notes from a past mech, for my (2003, 240K mi) Tundra to use non-synthetic oil.
NAPA-dude wants to sell me synthetic-blend, says that’s as close to non-synthetic you’re gonna get.
 
#1. I can’t imagine why your mechanic would want you to use only conventional oil over synthetic. They both have to meet a spec for viscosity and such, so I doubt the engine would notice as long as it’s the proper weight/viscosity. The primary difference is that the synthetics don’t break down as quickly as conventional which means longer oil change intervals and typically less chance of deposit buildups.

#2. Has the shop guy never heard of Castrol GTX or any number of other conventional oil brands?
 
I believe in using exclusively full synthetic oil in my car engines.

What does the manufacturer say?

Castrol 5-30 synthetic, 5 quarts for $25.00 shipped, Amazon.
 
I use full synthetic as well but on a high mile engine that doesn't require synthetic you are likely to get less leaks with conventional is my understanding of it...
 
Mobil says on their site to use caution switching from conventional to synthetic (reduced change interval for a while).
 
Let'sgoflying! said:
Mobil says on their site to use caution switching from conventional to synthetic (reduced change interval for a while).
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There are generally more/stronger detergents in synthetics, so a badly sludged motor will get that crud broken up and into suspension. Better to change more often while that is happening.
 
My new Jeep calls for a full synthetic.
 
Speaking of car oil and oil changes...

For those of you who change your own AIRCRAFT oil, you cut the filter to check for metal, send off a sample for analysis, right?

Do you do that with the car as well?

[Note: I don't change the car or airplane oil myself]
 
-KLB- said:
There are generally more/stronger detergents in synthetics, so a badly sludged motor will get that crud broken up and into suspension. Better to change more often while that is happening.
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Not sure if it’s the detergents, but the result is correct.

I took a 110k turbo V6 Buick that had conventional oil all its life, switched to synthetic and changed oil 3 times over a 3k mile period, because I kept opening the engine to make tweaks (oil pan gasket replacement, valve spring replacement, and oil pump mods). First oil change after synthetic was nasty. Last time I opened the engine, it was spotless, zero sludge, no exaggeration. Mobil 1. 1999-2001.
 
Ravioli said:
Speaking of car oil and oil changes...

For those of you who change your own AIRCRAFT oil, you cut the filter to check for metal, send off a sample for analysis, right?

Do you do that with the car as well?

[Note: I don't change the car or airplane oil myself]
Click to expand...

Yes.
No.
 
Sometimes on a higher mileage engines I’ve seen higher consumption rates with synthetic but normal/none for conventional. Usually the higher consumption happens between when you’d change conventional oil but synthetic isn’t due yet.

My suspicion is it’s a combination of oil getting older and thinner plus the synthetic being more uniform in weight vs conventional but that’s mostly speculation. I have observed the result pretty reliably though.

I say use the blend, check the level frequently, and if it’s fine then go with it.
 
Ravioli said:
For those of you who change your own AIRCRAFT oil, you cut the filter to check for metal, send off a sample for analysis, right?
Click to expand...
Yes
Ravioli said:
Do you do that with the car as well?
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No. If my truck has a catastrophic engine failure, I coast to the shoulder and make a phone call.
*Additionally, my trucks motor is a Duramax...not Continental/Lycoming
 
Big bore truck engines seem to be less critical on oil than small, high revving car engines. Your Cummins 5.9 L diesel will probably go half a million miles on conventional oil, so synthetic is kind of overkill. On a small, high revving car or motorcycle engine? Makes a big difference in life. If you're the kind of person that gets rid of a vehicle after it's a couple years old, I guess it doesn't matter. If you run them in to the ground like I do, use synthetic.

Edit: Agree with @Ted DuPuis
 
I'm not convinced a clean engine is good or necessary. I've been presented with no evidence that clean engines live longer or work better etc.

Also, the transition from 'sludged'....(sounds bad, but it's just goo in the recesses of the case)....to 'clean' seems to carry some risk.
 
The real need for synthetic oil comes on engines that have high localized stresses (pressures) and temperatures, which break down the oil. So for example my 3000GT VR4, BMW 740iL, and both the E55 and GL550 need synthetic. They’re engines that ask a lot of the oil and conventional breaks down too fast. Incidentally a similar concept applies at the turbine engine level - Mobil Jet II was fine on older engines but Shell 2380 is way better and doesn’t coke up as much. It just costs more.

I run conventional in the Ram, Rotella 15W-40. Like Sac said, should go half a million miles like that just fine. But I do 10k mile intervals instead of the 15k recommended.
 
Shell's Rotella has always been recommended as a good high-detergent oil. Especially valuable for the first couple of shorter-interval oil changes on a new-t-me older used car.
Plus, of course, the old trick of 'warm it up really well, add a quart of cheap ATF and let it idle for 10-20 minutes, then change the oil right away."
I'm definitely neither chemist nor engineer, so your mileage may vary. (Get it? Mileage may vary!)
 
My Duramax runs low oil pressure at idle when using synthetic. Even trips the low oil pressure alarm occasionally on synthetic. Doesn't do it with conventional so I use conventional in it.
 
FORANE said:
My Duramax runs low oil pressure at idle when using synthetic. Even trips the low oil pressure alarm occasionally on synthetic. Doesn't do it with conventional so I use conventional in it.
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My 2005 Duramax, the oil pressure is just fine at idle. I switched it to synthetic at 500 miles. How many miles on your truck?
 
Zeldman said:
My 2005 Duramax, the oil pressure is just fine at idle. I switched it to synthetic at 500 miles. How many miles on your truck?
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05 truck with 235k but changed motor about 15k ago for a topkick Duramax motor. Not really sure how many miles on the motor but it is a beast.
 
FORANE said:
05 truck with 235k but changed motor about 15k ago for a topkick Duramax motor. Not really sure how many miles on the motor but it is a beast.
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That sounds like worn bearings or a worn oil pump.
 
FORANE said:
05 truck with 235k but changed motor about 15k ago for a topkick Duramax motor. Not really sure how many miles on the motor but it is a beast.
Click to expand...

I gotta agree with Ted. Or possibly something not right with the sending unit.

What is the oil pressure at normal driving speeds?
 
Let'sgoflying! said:
Mobil says on their site to use caution switching from conventional to synthetic (reduced change interval for a while).
Click to expand...

My 2002 Suburban ran conventional and never leaked a drop of oil. I put in Synthetic and it started leaving a puddle of oil under it. Two days later I put conventional back in and it has never stopped leaking. I was warned of that on older vehicles.
That was 5 years ago and it still leaks.
 
pigpenracing said:
My 2002 Suburban ran conventional and never leaked a drop of oil. I put in Synthetic and it started leaving a puddle of oil under it. Two days later I put conventional back in and it has never stopped leaking. I was warned of that on older vehicles.
That was 5 years ago and it still leaks.
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In older vehicles, the natural rubber and fiber seals swelled by absorbing some of the oil, and synthetic isn’t absorbed as much in those materials, rendering a loose fit. But by 2000, that shouldn’t be a thing. It is also possible that a shaft seal had built up a layer of varnish on the shaft that the seal was riding on, and that the higher detergents took that shaft coating away, resulting in a loose fit. That could explain why switching back didn’t fix it. My 05 F150 has been on Mobil 1 since about 20,000 miles, and just within the last year has developed a rear main seal leak. Other than that, it seldom took any oil between extended oil change intervals. Not looking forward to dealing with that one. Debating actually paying someone to do it rather than deal with it myself.
 
My 7.3 with HEUI injection prefers synthetic, especially in the cold. Just switched to Rotella T6, 5W-40 fr the winter and it makes a huge difference in crank times...
 
Zeldman said:
I gotta agree with Ted. Or possibly something not right with the sending unit.

What is the oil pressure at normal driving speeds?
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With full synthetic (5w40) after warmed up at idle it could dip to the orange line on the gauge, what is that maybe 10-15 or so? With synthetic blend or 15w40 conventional it never hits the orange line.
When cold and when driving it is much higher, like 60.
I have replaced the sending unit a couple of times. Just replacing the sending unit has fixed low readings on this truck before.
 
FORANE said:
With full synthetic (5w40) after warmed up at idle it could dip to the orange line on the gauge, what is that maybe 10-15 or so? With synthetic blend or 15w40 conventional it never hits the orange line.
When cold and when driving it is much higher, like 60.
I have replaced the sending unit a couple of times. Just replacing the sending unit has fixed low readings on this truck before.
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The 15W-40, being a hair thicker, will impact that idle reading and that makes sense. That said, I've never heard of having to replace an oil pressure sensor that many times to get a reading up. Might be a Duramax specific thing, but that does sound like worn bearings or a worn pump.
 
I go with synthetic as two of the cars are modern turbo 4 cylinder engines. One is putting out 2hp/ci, the other 2.2hp/ci, far more than the old hot rodders goal of 1hp per cubic inch. As such, being turbo and high strung, I went synthetic at the 1st oil change.
 
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Costco now has "Kirkland" branded 5-30W synthetic oil. Something like $24 for 10 quarts
 
kgruber said:
Costco now has "Kirkland" branded 5-30W synthetic oil. Something like $24 for 10 quarts
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That there is a seriously good price!
 
pigpenracing said:
My 2002 Suburban ran conventional and never leaked a drop of oil. I put in Synthetic and it started leaving a puddle of oil under it. Two days later I put conventional back in and it has never stopped leaking. I was warned of that on older vehicles.
That was 5 years ago and it still leaks.
Click to expand...

I did same thing on my 04 burb but the transfer case- unknowingly. But turned out blessing in disguise. I didn’t know it had transfer case work done before and someone used the wrong sealant that worked for the 30 weight oil they put in it- I changed it not knowing they had done that and the T case fluid ate their seal!

In splitting it to do new seal I found out about “pump tub” a real killer to that era T case - $30 fix if ya catch it before it’s too late.. check into it- pretty simple repair to a factory oversight...
 
Huckster79 said:
In splitting it to do new seal I found out about “pump tub” a real killer to that era T case - $30 fix if ya catch it before it’s too late.. check into it- pretty simple repair to a factory oversight...
Click to expand...

Do you have a little more info on this? I have an 04' Sub, changed out the transfer case oil once, a long time ago.
 
SCCutler said:
That there is a seriously good price!
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I'd love to know how good it is. Kirkland gas is Top Tier, we run it in our cars with no issues. Never hurts that the gas is far cheaper than any other top tier rated stations and and with the Costo Visa card you get 4% back on all gas purchased at Costco. That makes it even a better deal than the cheapest no name gas.
 
my 2019 jeep has 8569 miles on it, the oil was changed at 5000 miles, the oil has not changed color, and still looks clear.
should I still change it, or can continue to run it ?

https://www.napaonline.com/en/p/NO_75521
 
Why would you change it after 3569 miles? Are we just talking age limit since last oil change? I don't think I'd change it out unless you get to two years without getting to oil change mileage interval. I only change the oil in the boat every other year since it usually only sees 10-15 hours of run time per year; that's with conventional not synthetic.
 
SoonerAviator said:
Why would you change it after 3569 miles? Are we just talking age limit since last oil change? I don't think I'd change it out unless you get to two years without getting to oil change mileage interval. I only change the oil in the boat every other year since it usually only sees 10-15 hours of run time per year; that's with conventional not synthetic.
Click to expand...
the plan was to change at 5k
 
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