Using 15w40 instead of 10w30

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Jul 14, 2020
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My situation is, I have a full 5 gallon bucket of Traveler (TSC) 15w40 conventional oil (SN). I have a 1998 Mustang with the 3.8 engine with only 79000 miles on it. Ford calls for 10w30 in it, but I am wondering if I could use the 15w40 in it? The thing is, this car sits in my attached garage, and basically doesn't get driven in the winter. It will probably never get started if the temp is below 50 degrees F.
IF you think that would be a little to thick for it, would it be ok to mix it with some 5 or 10 30 that is a different brand??

If neither is a good idea, I will save it to use in my 65 mustang 6 cylinder or my lawn mowers I guess.
 
Thanks for the go ahead. I thought so, but just wanted to check with you guys.
 
My situation is, I have a full 5 gallon bucket of Traveler (TSC) 15w40 conventional oil (SN). I have a 1998 Mustang with the 3.8 engine with only 79000 miles on it. Ford calls for 10w30 in it, but I am wondering if I could use the 15w40 in it? The thing is, this car sits in my attached garage, and basically doesn't get driven in the winter. It will probably never get started if the temp is below 50 degrees F.
IF you think that would be a little to thick for it, would it be ok to mix it with some 5 or 10 30 that is a different brand??

If neither is a good idea, I will save it to use in my 65 mustang 6 cylinder or my lawn mowers I guess.

Technically Ford currently calls for 5W-20 in the '98 3.8L Mustang.

That oil is about 14.5 cSt at 100C and 5W-20 is roughly 8.5 cSt so I would mix those two 50/50 which would give you roughly 11.0 cSt or similar to current API 5W-30 or 10W-30 oils. Just pick up some Taveller's, Supertech or Chevron or whatever 5W-20 you can get cheap to make your own 10W-30.
 
And... why does Ford "technically" call for 5w-20? Any ideas?

Why would I speculate. That doesn't need rehashed. I was just clarifying the current recommendation. I wouldn't have brought it up if the OP hadn't posted "Ford recommends 10W-30".

I suggested how to use his 15W-40 and get essentially the same viscosity as his preferred 10W-30.
 
My statement of ford recommending 10w30 is from the owners manual that came with the car. I am asking about using the 15w40 because I have it, and want to use it up. I also have 10w30, that is in it now. Also, I am sort of a believer of thicker oil rather than the new trend to thinner oils. UNLESS the thicker oil would cause a problem. And I don't mean loss of a tiny bit of fuel mileage.
 
Unless the oil’s winter rating is so inappropriate for the starting temperature that it cannot be pumped there is no way it will be so thick as to cause an issue. And this is only a bump of one grade. It’s not going to be a problem.
 
Technically Ford currently calls for 5W-20 in the '98 3.8L Mustang.

That oil is about 14.5 cSt at 100C and 5W-20 is roughly 8.5 cSt so I would mix those two 50/50 which would give you roughly 11.0 cSt or similar to current API 5W-30 or 10W-30 oils. Just pick up some Taveller's, Supertech or Chevron or whatever 5W-20 you can get cheap to make your own 10W-30.
So You are saying that it would be ok to thin the 15w40 down with 5w20 as long as I use Warren oil to do it and not to use any other manufactures oil to thin it down??
 
So You are saying that it would be ok to thin the 15w40 down with 5w20 as long as I use Warren oil to do it and not to use any other manufactures oil to thin it down??

No Chevron is not a WPP product. I simply meant an oil that made sense from a financial standpoint. It will use 40 grade okay with only a slight loss if fuel mileage. My point was simply if you prefer 30 Grade no reason not to blend the 15W-40 and a 5W-20 50/50 to get your preferred grade. One of the requirements of approval is the ability to be mixed with other approved oils.
 
My situation is, I have a full 5 gallon bucket of Traveler (TSC) 15w40 conventional oil (SN). I have a 1998 Mustang with the 3.8 engine with only 79000 miles on it. Ford calls for 10w30 in it, but I am wondering if I could use the 15w40 in it? The thing is, this car sits in my attached garage, and basically doesn't get driven in the winter. It will probably never get started if the temp is below 50 degrees F.
IF you think that would be a little to thick for it, would it be ok to mix it with some 5 or 10 30 that is a different brand??

If neither is a good idea, I will save it to use in my 65 mustang 6 cylinder or my lawn mowers I guess.

#1 Why do you have a 5 gal bucket of Traveller 15W40?

#2 Yes you can use the 15W40 in all the vehicles/appliances described

#3 Your 3.8 will have even less power than it has now due to excessive windage

Is your 1998 'Stang a convertible to enjoy in the Summer?
Is it a Stick shift or Auto?

Enjoy!
 
Technically Ford currently calls for 5W-20 in the '98 3.8L Mustang.

That oil is about 14.5 cSt at 100C and 5W-20 is roughly 8.5 cSt so I would mix those two 50/50 which would give you roughly 11.0 cSt or similar to current API 5W-30 or 10W-30 oils. Just pick up some Taveller's, Supertech or Chevron or whatever 5W-20 you can get cheap to make your own 10W-30.
This is what I would do.....'Traveller' is (at least it once was) made by WPP)...so I'd mix it with ST conventional.
 
#1 Why do you have a 5 gal bucket of Traveller 15W40?

#2 Yes you can use the 15W40 in all the vehicles/appliances described

#3 Your 3.8 will have even less power than it has now due to excessive windage

Is your 1998 'Stang a convertible to enjoy in the Summer?
Is it a Stick shift or Auto?

Enjoy!
I have a 5 gal bucket because I had a couple vehicles at the time that it would have been perfect for, and they had a really good sale.
It is not a convert
It is an automatic
 
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