Switching to Pennzoil Synthetic on a 03 Subaru Legacy?

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Dec 12, 2023
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I have a low mileage 2003 Subaru Legacy wagon with 43k miles. It’s only ever had straight conventional Pennzoil or Synthetic Blend Pennzoil. Would it be a mistake or waste of money to switch it to full synthetic at this point? I would would stick with Pennzoil products but just change to Platinum or Ultra Platinum.
 
What are you expecting the switch to accomplish? . I can't see any notable benefits other than marketing claims.
 
taking it a step up to a full synthetic like the Pennzoil Platinum would be a good choice ,only a couple of dollars more and better engine protection ,maybe use 5w-30 and good filter,changing out every 5k intervals,good price at Wall mart too.
 
Pennzoil Platinum does have a pretty good rebate right now, a $25 gift card on 2 five quart jugs. Catch it on sale, it’s a pretty good deal, too. The current Meijer sale would make 2 jugs ~$24 AR, cheaper than PYB!
 
Owned several of that vintage EJ, it will be fine using synthetic.
 
I switched to synthetic on an old high mile vehicle in the past with no problem. So no, it shouldn’t be a mistake. Waste of money? You could decide not to drive down the road and save a 1/2 gal of gas and makeup the cost difference between the least expensive blend and synthetic spread over 6 months of use. It’s just a question of “is it worth it to you”.
 
I would try Pennzoil Platinum. A better oil should give you the peace of mind to go a bit longer between oil changes, especially if it's a synthetic that meets Dexos1 Gen3. You'll probably get slightly better fuel economy as well. These factors might completely offset the increased cost of the oil.
 
I would try Pennzoil Platinum. A better oil should give you the peace of mind to go a bit longer between oil changes, especially if it's a synthetic that meets Dexos1 Gen3. You'll probably get slightly better fuel economy as well. These factors might completely offset the increased cost of the oil.
The reason I’m thinking of doing this is 2 fold. One reason is the rebates that Pennzoil has been having. I have another car that uses 5w30 that currently uses Pennz Ultra Platinum. The other reason is due to some recent medical issues I might not be able to do my own oil changes but there is a garage near me that has really good oil change prices and they only use Pennz Platinum. I’ve heard that switching over to synthetic in an older car can sometimes result in oil leaks from the thinner synth oil.
 
The reason I’m thinking of doing this is 2 fold. One reason is the rebates that Pennzoil has been having. I have another car that uses 5w30 that currently uses Pennz Ultra Platinum. The other reason is due to some recent medical issues I might not be able to do my own oil changes but there is a garage near me that has really good oil change prices and they only use Pennz Platinum. I’ve heard that switching over to synthetic in an older car can sometimes result in oil leaks from the thinner synth oil.
No. Synthetic oil is not thinner per grade. Grade is determined by the grade not by the base oil composition.
 
I’ve heard that switching over to synthetic in an older car can sometimes result in oil leaks from the thinner synth oil.
I wouldn't say that it's impossible for oil leaks to develop due to switching to a synthetic oil, but it wouldn't be due to the viscosity.

Synthetic oils containing PAO can in theory cause problems with seals, though they should contain seal conditioners to counteract this. In any case, PP and PUP don't contain much if any PAO.

When switching oils, it's always possible that the new oil with have worse seal compatibility for a given engine, and if a leak develops, you'll hear complaints about the new oil. It's also possible to switch to an oil with better seal compatibility, but you're unlikely to hear stories about these cases. This doesn't have anything to do with whether the oils are conventional or synthetic. Switching to PP could make leaks more likely, less likely, or it could make no difference.
 
I don't think I could bring myself to use conventional oil today. Especially if you intend to keep the vehicle for an extended time.
I'm sure conventional oil would be just fine.
 
I don't think I could bring myself to use conventional oil today. Especially if you intend to keep the vehicle for an extended time.
I'm sure conventional oil would be just fine.

Considering how cheap you can get Supertech or Kirkland synthetic it really makes no sense to use conventional oil unless you’re finding a crazy clearance deal for $2 a quart or less. And even then I personally wouldn’t use it. I can’t even remember the last time I used conventional oil. It was long before I was on BITOG.
 
Considering how cheap you can get Supertech or Kirkland synthetic it really makes no sense to use conventional oil unless you’re finding a crazy clearance deal for $2 a quart or less. And even then I personally wouldn’t use it. I can’t even remember the last time I used conventional oil. It was long before I was on BITOG.
I started my synthetic oil journey in the mid 70's with the original M1 5w-20. It was $6.00 US a quart!!!
 
I started my synthetic oil journey in the mid 70's with the original M1 5w-20. It was $6.00 US a quart!!!

I first bought M1 10w30 in 1988, at that time I could only get it at an Esso station and it was $5 a liter, compared to $1 a liter for Castrol XLR.
 
I wouldn't say that it's impossible for oil leaks to develop due to switching to a synthetic oil, but it wouldn't be due to the viscosity.

Synthetic oils containing PAO can in theory cause problems with seals, though they should contain seal conditioners to counteract this. In any case, PP and PUP don't contain much if any PAO.

When switching oils, it's always possible that the new oil with have worse seal compatibility for a given engine, and if a leak develops, you'll hear complaints about the new oil. It's also possible to switch to an oil with better seal compatibility, but you're unlikely to hear stories about these cases. This doesn't have anything to do with whether the oils are conventional or synthetic. Switching to PP could make leaks more likely, less likely, or it could make no difference.
Which synth oils contain POA? Is it listed on the bottle?
 
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