Whats the advantage of syn blend?

Joined
Feb 18, 2022
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Hey all. I'll try to keep this brief. I've ran Dino oil I everything I've owned, all my life. I currently have a 1989 chevy 1500, 350 c.i. As with most older trucks, it consumes an amount of oil, mostly burns it through the valve seals and there's a slight rear main leak. So far I've found it to tolerate castrol GTX 10-40 far better than anything lighter, or any other brand.
Anyway, I've really liked the idea of switching it over to a high mileage oil, to try and swell some of the seals up before I have a chance to remove the engine and rebuild it. My only problem is I know the stories of guys switching to full syn, and what was once a little drip beneath their truck turned into a puddle. I'm not sure if a syn blend would have the same effect. I'm used to having to keep an eye on my dipstick, but I don't want to be going through ludicrous amounts of it. That's just not economical, when running Dino at regular OCIs is more than good enough. Is there any advantage to switching over to a high mileage syn blend or should I just stick with conventional? Thanks.
 
Joined
Apr 7, 2019
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VA
Really right now conventional oils are going by the wayside, to meet the new specs it takes at least a blend to be able to meet them. Yes you can switch from conventional, blend, full synthetic, high mileage, etc... at any time now back and forth without issues. I think you should try Valvoline Maxlife Synthetic Blend, all the reviews I've read online state that it's the best for a leaking rear main seal.
 
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My only problem is I know the stories of guys switching to full syn, and what was once a little drip beneath their truck turned into a puddle.


Those stories have been around since the beginning with Mobil 1.

Run a good high mileage oil.

Lots of recents threads on this exact subject. You might find answers in those.
 
Joined
Oct 22, 2009
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I switched my 2004 Corolla over to synthetic at 60K something miles. Switched back and forth from full synthetic and HM oil several time the ole wives tail never reared it head. YMMV.
 
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In the piston aircraft world, there is one commonly available semi-synthetic oil, Aeroshell 15W-50. Which as I understand it, is roughly 1/2 PAO synthetic and 1/2 dino oil. Additive packages are very modest and nothing like car oils. No ZDDP or viscosity index improvers, as I understand it.

What is interesting is that the varnish buildup is considerably lower, but not eliminated. I've got an engine using this oil with 800 hours of use and the varnish is lower. Also of note, the oil sump remains clean. Conventional oils will build up sludge in the sump of these engines.
 
Joined
Nov 2, 2021
Messages
1,117
Hey all. I'll try to keep this brief. I've ran Dino oil I everything I've owned, all my life. I currently have a 1989 chevy 1500, 350 c.i. As with most older trucks, it consumes an amount of oil, mostly burns it through the valve seals and there's a slight rear main leak. So far I've found it to tolerate castrol GTX 10-40 far better than anything lighter, or any other brand.
Anyway, I've really liked the idea of switching it over to a high mileage oil, to try and swell some of the seals up before I have a chance to remove the engine and rebuild it. My only problem is I know the stories of guys switching to full syn, and what was once a little drip beneath their truck turned into a puddle. I'm not sure if a syn blend would have the same effect. I'm used to having to keep an eye on my dipstick, but I don't want to be going through ludicrous amounts of it. That's just not economical, when running Dino at regular OCIs is more than good enough. Is there any advantage to switching over to a high mileage syn blend or should I just stick with conventional? Thanks.
Cars that have fuel dilution and require shorter oci’s
 

wlk

Joined
Aug 21, 2016
Messages
205
Location
Pennsylvania
I run Quaker State High Mileage 10w40 blend in my 93 C1500 5.7l and a bottle of Schaeffer Moly EP and that has cut my leaks down a lot. Drips are gone from the driveway and it uses/leaks about .5qts per 5k mile oci down from 1-1.5qts. The Moly EP makes it about a 50w oil as it is thick and I put the whole 16oz in w a 5qt jug. Don't waste your time w Lucas I tried a couple times thinking the thicker additive was it but it still used the 1 to 1.5qts The Moly EP and HM Quaker State seem to work well in it, worth the 15 bucks the Moly EP costs
 
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Joined
Jun 15, 2020
Messages
33
Location
Aitkin,MN,USA
I switched my 2004 Corolla over to synthetic at 60K something miles. Switched back and forth from full synthetic and HM oil several time the ole wives tail never reared it head. YMMV.
I agree. Synthetic does Not run through high mileage seals more than conventional or blends. It appears we have two choices for 0w30 syn high mileage. I am considering adding at205 to create high mileage. Anyone?
 
Joined
Dec 26, 2005
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Upper Midwest
I agree. Synthetic does Not run through high mileage seals more than conventional or blends. It appears we have two choices for 0w30 syn high mileage. I am considering adding at205 to create high mileage. Anyone?
You should go to work for Infineum or Lubrizol. Think of the money you could save them.
 

Patman

Staff member
Joined
May 27, 2002
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Location
Guelph, Ontario
I have always felt like synthetic blends were just a way for the oil companies to charge a lot more money for a product that really isn't any more "synthetic" than the conventional oil that they sell for considerably less money. If they actually were made with 50% of it's base oil as synthetic it might make sense, but most semi synthetics are nowhere near that level.
 
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Jun 8, 2021
Messages
221
Location
Columbus, OH
Mostly its just more affordable. I used Motorcraft synth blend for years in my F-150 and always felt like it performed pretty well. If I had a vehicle that didnt do extended oil change intervals, blend might be worth considering because it has some of the advantages of a full synthetic without the cost.
 
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