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Real or Myth?: Syn vs. Conv.

O'Rattlecan

Redneck Prognosticator
26,687
797
Belton, MO
Fact or Fiction?:

Synthetic oils tend to burn less over a similar oil life to a conventional oil.

Someone give me some info here.

Ryan
 

taxreliever

Licensed to Represent!
14,695
287
Maine
Lester seems to be super knowledgeable in this area......subscribed as I'm interested as well!
 

DNFXDLI

The Token Canadian
Staff member
I could answer but I won't...I use a particular brand that I am very happy with.
All I will say is that true synthetic will tend to hold up better all the way around...and also, the crapola about not using synthetic for engine break-in is a crock...given that several manufacturers use it from day one in specific models.
 

O'Rattlecan

Redneck Prognosticator
26,687
797
Belton, MO
I know that there are caveats when it comes to 'synthetic' but I'm speaking more at a theoretical level than I am trying to get down in the weeds.

I was wondering because I use the motorcraft synthetic blend in my truck. Over the life of the oil, I burn over quart. I was thinking about doing a little experiment and seeing how much of a pure synthetic oil would burn off compared to my low cost blend.

Ryan
 

DNFXDLI

The Token Canadian
Staff member
I didn't understand what you meant by "burn less"...I thought you were referring to actual burning/sludging of the oil.
 

73F100Shortbed

That's how we roll!
5,937
320
NJ
Lester will have to chime in on this one. He had some good info with his last comment about oil. I was going to use synthetic when I put my new engine in but I'm glad I didn't because the leak I have still causes me to add a quart of oil every so often <rant>(Thanks for nothing Autozone!)</rant>
 

O'Rattlecan

Redneck Prognosticator
26,687
797
Belton, MO
I meant very literally, "Will I have more oil when I do my next change if I use synthetic?"

I have heard that if you use synthetic less of it will burn off.

I use 6 quarts of conventional oil, and when I do my oil change, 4.5 or 5 quarts comes out.

If I use 6 quarts of synthetic, will mabye 5 or 5.5 quarts come out in the same span of miles?

Ryan
 

DNFXDLI

The Token Canadian
Staff member
Personally, I have never noticed a difference. I have never really checked other than what appears on the dipstick.
 

73F100Shortbed

That's how we roll!
5,937
320
NJ
You never top off your oil between oil changes? When I do my oil change 5 quarts goes in and 5 quarts comes out. I don't think I could drive around with it being 1.5qts low.
 

O'Rattlecan

Redneck Prognosticator
26,687
797
Belton, MO
If I think about it, I might add a half quart here or there. I change my oil so often (I drive quite a few miles) that I usually don't get around to it.

I've never burned up a bottom end of a motor and drive high mile vehicles my whole life, so I'm not that concerned about it. I am a little more curious if that oil would last a little longer in the crankcase though...

Ryan
 

taxreliever

Licensed to Represent!
14,695
287
Maine
I meant very literally, "Will I have more oil when I do my next change if I use synthetic?"

I have heard that if you use synthetic less of it will burn off.

I use 6 quarts of conventional oil, and when I do my oil change, 4.5 or 5 quarts comes out.

If I use 6 quarts of synthetic, will mabye 5 or 5.5 quarts come out in the same span of miles?

Ryan

This is what I've heard in the past but have never put it to the test.....if one of my vehicles leak, only the cheap stuff goes in there like my POS cheby plow truck, but all of our other vehicles (not the bump yet, want to go through a few changes when I use it more to get used to it and make sure there are no leaks - so far so good, and still may just keep cheap stuff in there - wanted to ask you fellas when the time came).

Our family car has had both the regular oil and now synthetic, but it has never burned any (i've never had to top it off with either).

You never top off your oil between oil changes? When I do my oil change 5 quarts goes in and 5 quarts comes out. I don't think I could drive around with it being 1.5qts low.

For the vehicles that do burn, I always top it off every other fill up or so depending on how often that particular vehicle burns oil....right now I only have one.
 

LEB Ben

Arrogant A-hole At-Large
34,919
1,124
outside your house
I can't answer your exact question Ryan, but when I've had good running, non-leaking engines, I've never noticed a difference. However, when I had the old 351M in the Bronco, and rings were toast and valve seals were gone, I can honestly say, I went through, without a doubt, more synthetic oil than I did dino style. That said, I believe most of the negative said about synthetics these days are based off old assessments, still perpetuated today.
 

taxreliever

Licensed to Represent!
14,695
287
Maine
Where's Lester...I want to hear his input on this....
 

Fellro

Moderator
Staff member
I was going to use synthetic when I put my new engine in but I'm glad I didn't because the leak I have still causes me to add a quart of oil every so often <rant>(Thanks for nothing Autozone!)</rant>

Just have to ask, how is it their fault? what kind of leak do you have?

My understanding is that you would use less oil to vaporization, as the oil withstands the heat a bit better. I had in the past run the Wally World Super Tech, and would lose a quart per change. I quit using that, and went to Havoline, and stopped losing as much, very little per change. That was even with leaking valve seals. i figure it was going out as vapor.
 

lil_dq

Let 'er eat boys!
6,933
265
Union, MO
Here is what my engine guy told me...

Imagine oil as change in you pocket...

Synthetic is lets say all dimes, where as conventional oil is a managery of change. A few quarters, nickles, dimes and pennies.

Now lets say you have an older motor with a few miles on it (your pocket). If you have a small hole that a dime size molecule will fit through and you have synthetic in there, it will burn/leak a lot easier as it is all exactly the same size. If you have conventional oil in there one of the quarter sized molecules could slide up to the hole and plug it.

IDK if that is the case or not, but it seems to make "cents" (haha)...
 

Fellro

Moderator
Staff member
Nice analogy, kinda the way I understand it as well.
 

blackhat620

You Had to be There
1,687
150
Arizona
Fact or Fiction?:

Synthetic oils tend to burn less over a similar oil life to a conventional oil.

Someone give me some info here.

Ryan

Maybe depending on operating conditions & load (think Death Valley July towing 15K daily) but generally for most dd users you will not see a difference.

I know that there are caveats when it comes to 'synthetic' but I'm speaking more at a theoretical level than I am trying to get down in the weeds.

I was wondering because I use the motorcraft synthetic blend in my truck. Over the life of the oil, I burn over quart. I was thinking about doing a little experiment and seeing how much of a pure synthetic oil would burn off compared to my low cost blend.

I meant very literally, "Will I have more oil when I do my next change if I use synthetic?"

I have heard that if you use synthetic less of it will burn off.

I use 6 quarts of conventional oil, and when I do my oil change, 4.5 or 5 quarts comes out.

If I use 6 quarts of synthetic, will mabye 5 or 5.5 quarts come out in the same span of miles?

Ryan

No you will not have more oil at your next oil change. Currently you are using a "semi-synthetic", the switch to a "full synthetic" (Group III, IV or V) or "full conventional" is not going to appreciably change your engines oil comsumption. The only thing that would change your oil consumption by changing oil types is if the "new" oils chemistry causes new leaks in your engine and the odds of that with todays oils are slim at best.
A much greater effect on the dd oil consumption is the choice of oil viscosity, low viscosity oil use generally results in higher consumption levels, and less barrier protection under load.

A synthetic oil (Goup III, IV or V) has and advantage in extreme cold (Alaska) and extreme heat (Death Valley). The advantage to synthetic oil in extreme cold is that it is more stable & flows better in low temperatures than dino oil. This is one of the main reasons synthetic oil was developed. In extreme heat synthetic oil has a higher flash point (important for turbine engines) and has better "barrier" protection than dino oil.

Manufactures specify low oil viscosity to get a slight uptick in mpg which is important in meeting government mandates cheaply and it also will increase engine power output slightly but at the added cost of more wear. The specification of low viscosity oils by the manufactures has resulted in the increased use of "semi-synthetic" & "full synthetic" oils in order to meet the minimum lubrication requirements of the engine, since most dino oils at 5W-20 etc do not have the stability to work consistantly under normal driving conditions.

Ryan this is a quick Cliff Notes version hopefully it helps.
 
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