Best oil weight to use

[Lazerred98]

Ok, so I am new to this forum, and new to sn95 mustangs, even though I was a mechanic in 1965 at a ford dealer, and have owned a 65 with 200 6 cyl for past 12 years, and had a 2005 v/6 for a couple years a couple years back. Just a year ago I bought a 98 6 cyl with 78000 miles on it and in very nice shape. Then the Covid hit, and I have driven it very little since. Went to a couple judged shows, and got a trophy in each. I changed the oil right after bringing home, and put in 10w30 conventional oil. When I change oil again I will probably use high mileage oil, as it has a slight seep somewhere, but since the owners manual says 5w30, should I use that or stick with the 10w30? I understand that ford actually back spaced it to 5w20, but that was surely just for CAFE. So what say you guys, 5w30 10w30 or even 10w40, or I have some 15w40 conventional. All the others will be semi synthetic and high mileage except the 15w40.

 

[dwcopple]

6w

 

[Connie]

Ok, so I am new to this forum, and new to sn95 mustangs, even though I was a mechanic in 1965 at a ford dealer, and have owned a 65 with 200 6 cyl for past 12 years, and had a 2005 v/6 for a couple years a couple years back. Just a year ago I bought a 98 6 cyl with 78000 miles on it and in very nice shape. Then the Covid hit, and I have driven it very little since. Went to a couple judged shows, and got a trophy in each. I changed the oil right after bringing home, and put in 10w30 conventional oil. When I change oil again I will probably use high mileage oil, as it has a slight seep somewhere, but since the owners manual says 5w30, should I use that or stick with the 10w30? I understand that ford actually back spaced it to 5w20, but that was surely just for CAFE. So what say you guys, 5w30 10w30 or even 10w40, or I have some 15w40 conventional. All the others will be semi synthetic and high mileage except the 15w40.

With our '03 GT and '04 Mach1, as time went on and the engines broke in, I thought the tolerances loosened up enough to go to 5W-30 after the third Oil Change. Instead of staying with the 5W-20. Of course that assumption is only in my own mind. I stayed with the 5W part because, I felt under cool engine conditions the Oil needs to reach all the internals without slowing the flow. I changed to the 30W side, believing the tolerances could handle the heavier weight after engine warm up, after the break in period. But, that's only my theory. After 18 years it hasn't hurt. Bob.

 

[Lazerred98]

6w

LOL, 6w what? 30 or 40

 

[Frank.JD.Perez]

depends on what you use your car for and the climate where you live. 5w20 should be fine 9 times out of 10. in the warmer months if you drive the car a lot and its stupid hot then jump up to 5w30. be sure to use quality oil and oil filter too. before my new engine i used motorcraft synthetic blend 5w20 and never had an issue. still use a motorcraft filter too

 

[PinkieT]

You can't go wrong sticking to using a quality oil of the Ford recommended viscosity. I used to work in an auto parts store and sometimes customers would insist on putting 10W-40 in their 0W-20 2020 Civic in the summer because that is what they or their dad put in their Galaxie 500 back in the day. Yeah, I would sell it to them if they insisted, but I wouldn't top off their car for them. Like Bob suggested, maybe 5W-30 on a worn SN95 engine, but personally I wouldn't vary any further from the factory spec oil. Just my .02 worth.

 

[Lazerred98]

You can't go wrong sticking to using a quality oil of the Ford recommended viscosity. I used to work in an auto parts store and sometimes customers would insist on putting 10W-40 in their 0W-20 2020 Civic in the summer because that is what they or their dad put in their Galaxie 500 back in the day. Yeah, I would sell it to them if they insisted, but I wouldn't top off their car for them. Like Bob suggested, maybe 5W-30 on a worn SN95 engine, but personally I wouldn't vary any further from the factory spec oil. Just my .02 worth.

Well. since the owners manual that came with the car says to use 5w30, and doesn't even specify if conventional or semi synthetic, or full synthetic, I would think that 5w30 semi synthetic should be fine, if it was recommended by ford when the car was new. I am considering 10w30 due to the fact that it may be a little more stout oil due to not having as many vi improvers in it, and I NEVER start the car below 50 degrees f.

 

[PinkieT]

Sorry, I was thinking about another car I own. My 98 GT owner's manual and the sticker under the hood both call for 5w30. That is what I personally will stick with. 10w30? I got no problem with that. 10w40 or 15w40? Not a fan. Amsoil has a pretty good explanation web page covering this: https://blog.amsoil.com/what-happen...ker oils don't,viscosity, check out this post.

 

[Frank.JD.Perez]

i dont think synthetic existed back in the 90s... i could be wrong though

 

[Lazerred98]

i dont think synthetic existed back in the 90s... i could be wrong though

I know for sure Amzoil was around, but I am not sure when the other companies came out with synthetic. I think probably Mobil1, then others. I am so old that the 90's seem like just a couple years ago to me.

 

[PinkieT]

From my training and what I've read, modern synthetics are fine in older cars.

 

[Frank.JD.Perez]

lol

i would recommend the motorcraft synthetic blend just my $1.02

 

[D3VST8R96GT]

I would use full synthetic.
5w or 10w is more than fine. I think 40 is a little thick but it won't matter too much if your not bouncing off the redline or running it hard and low on oil.

 

[07GtS197]

This thread got derailed fast lol. The op is driving it very little and it’s not a racecar. I agree, factory spec motorcraft and motorcraft filter. No need to go crazy.

And for the leak find out where it’s coming from and fix that. Changing oil viscosity and switching to synthetic is a band aid.


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[ttocs]

Derailed? Its all been about oil and what people use and like which is what he asked.

 

[Frank.JD.Perez]

slightly off topic. maybe not derailed. i DO race my car and i still use the same parameters that ford intended. 5w20/5w30. OP should run synthetic blend or full conventional 5w20 or 5w30 depending on driving habits.

i would suggest that the OP do an oil change and once all the oil is out to check the oil pan gasket and the factory oil cooler gasket as these cars are old and those are more than likely the original gaskets in there. once those bad boys get changed then just run whatever you want for oil. just keep in mind it is a factory 20+ year old engine that was made to work with conventional oil. theres the remaining .98

now you have $2.00 lol

 

[07GtS197]

I meant derailed in the sense people are talking about synthetic vs conventional and different weights. Let me clarify, I think it went overboard not derailed. Lol.


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[RAU03MACH]

synthetic will make it leak more because its a lot finer oil not a thicker oil
5 30 regular Valvoline is good

 

[Frank.JD.Perez]

This guy

Knows what he's talkin bout

 

[white95]

Mustang go brrrr

You won’t notice much difference switching to semi or full synthetic at this stage in your cars life. Simply use the cheapest, recommended spec oil and enjoy the ride.

Oh, and I’d fix the leak.