Curious as I have a 1992 Mustang 5.0 and drive it fairly hard at times. The books says run 10w30 in hotter weather. I have a lot of Maxlife 5w30 synthetic blend that I bought maybe 5 years ago. I am thinking that a modern 5w30 has to be as tough as an early 1990s 10w30 and, if so, there is no reason not to run the Maxlife 5w30 in the Mustang. Your thoughts?
How does a modern 5w30 compare to a 1990s 10w30
- Thread starter TallPaul
- Start date
Check for any TSB's. My '93's book calls for 10w-30 but was later changed to 5w-30 in a TSB.
You will be fine with 5w-30. 5w-30 and 10w-30 are both 30 grades at operating temperature.
You will be fine with 5w-30. 5w-30 and 10w-30 are both 30 grades at operating temperature.
That a 5w30 has more viscosity improver polymer chains than a 10w30 does not matter?
When I plugged the 1992 Mustang into the Amsoil vehicle look up tool, it says 5W-30 all temps on the 5.0. I know I have seen it say specs were updated with a TSB on other vehicles when using their vehicle look up tool. My guess is that was said in the 90s but with the oils we have today, it is irrelevant.
There is a huge difference between the SL oil recommended in 1992 to oils of today.
Ok, great, thanks! I won't have to buy any oil for a long time for the Mustang even though it is passing a quart through the exhaust every 280 miles, mostly the driver side rear cylinder.
I bet it’s like comparing your 5.0/302 to a 5.0 Coyote motor
I have no idea how that would go. The Coyote is a totally different engine and probably takes a 5w20. But I am old school and love those old pushrod engines.
I'll just add that in spite of the huge oil consumption, the car runs like a champ. It's got 156,000 miles on it. I had some trouble with the left rear plug fouling, but put in a non-fouler with an E3 Plug and the car runs great (1300 miles and still not fouled). This year, after an engine flush with the Amsoil product, it is running better than ever. Back in 2023 I would get oil smoke wafting past me at a stop light on a breezy day. Now I hardly notice the smoke.
So you’re adding a quart of oil about every 300 miles? Sounds like a good candidate for Valvoline Restore and Protect.
You, my friend, are definitely not alone
Yep a quart every 300 easily. What is a Valvoline Restore and Protect?
At this point, she would not light up the tires anymore. This was before I got the non-fouler.
AZjeff
$50 Site Donor 2023
See? That's why you spell it out.
Valvoline Restore and Protect. At the number of miles it is driven it would take forever to do anything.
This is a good example why product name abbreviations aren’t a good idea.
This is a good example why product name abbreviations aren’t a good idea.
Yep, we ran the Valvoline Restore and Protect in 2025. Curiously it did not foul the plug all 2023 or 2024 (BTW, the car is only driven in fair weather, so about April through October). That's about 2000 miles. After I put the Valvoline Restore and Protect in is when the plug fouled. I cleaned that plug off, car ran great again, but plug fouled in only 15 miles. The non-foulers really work by moving the spark plug about half an inch out from the combustion chamber. It has not fouled since and that is about 1300 miles with the non-fouler installed. This year I did the Amsoil engine flush and filled with Maxlife 10w30. This year I see less smoke than ever, in fact, hardly notice it.
FWIW, I've had my '93 5.0 coupe for over 20yrs. For the first 18years it was fed a steady diet of Mobil 1 10W-30 and Mobil 1 filters. The car liked it just fine and ran like a top. Then I switched to Mobil 1 0W-40 and the change was noticeable, quieter valvetrain and better oil pressure at idle as to be expected. I also switched to FRAM XG8A's as the Mobil 1 filters became hard to source for whatever reason.
These engines have very loose clearances by today's standards and appreciate a thicker oil with a higher HTHS and better film strength. My car has ~128,000kms on it as of today and doesn't require top-off's between changes and also sees some spirited miles every time it's out. 10W-30, 5W-30 are both fine...I've owned a few Fox Stangs and a 40 weight feels right in them IMO
It currently has a fresh sump of Mobil 1 Extended Perfomance High Mileage 5w30 that I got a great deal on. These engines aren't super picky and will run on anything but the tick they all seem to have on thin oil is negated by a 40 weight, at least in my experience.
Welp, I ran a 15w40 in 2024 and it smoked worse than ever. Also, with the Valvoline Restore and Protect 5w30 the oil pressure tested to spec, about 44 psi at 2000 rpm on the road. I ran 10 miles with some spirited runs on a day in the 80s in order to get the oil good an hot. Here is the pressure test setup. I just drove it around like this for about half an hour:
That's bad. Amazing the plug doesn't foul out.
How much MaxLife do you have and how many quarts is your sump?
Is that flat-tappet cam engine?
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