Question about synthetic oil

TheCrazy1

New Member
Dec 8, 2003
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This is more a question of opinion, I suppose...here's the deal. I have a 98 Cobra with 110k miles on it and I used Mobil 1 synthetic oil for the last oil change. I noticed the oil consumption went up significantly. With conventional oil it would go through about 1 quart in a 3000 mile interval. But with the synthetic it's gone through nearly 2 quarts in 3000 miles. I was wondering if I should continue with the synthetic oil or go back to standard petroleum oil. I always use Valvoline or Castrol 5w30, by the way; with a Bosch filter. What do you guys think? Thanks in advance... Leo
 
If the consumption level is going up and you have no signs of oil leaks or blue smoke out the tailpipe (ie - mechanical problems), you're probably better off just sticking with conventional oil. Two quarts per 3000 miles is a bit much IMHO.
 
Yah, 2 quarts is a bit much compared to only about 1 with regular oil. I may give a semi synthetic a try next time around. I've seen Ford engines go over 250k miles on regular oil at the dealers I've worked for. They just changed it regularly and they kept on runnin! Thanks for the advice. Hopefully it doesn't keep using the larger amount when I do switch back! d'oh!!!
 
Yeah, don't waste your money and spend time worrying. Go back to conventional. I use conventional in my 96 Cobra with the Vortech with no problems at all. I have heard of your problem before, and that same person switched back to conventional and his car was fine.
 
Dr. Wu 2000 said:
You can just switch back to conventional after useing synthetic for all that time??? I thought that was a no-no.
Naw.... You can actually mix a full synthetic with a dino oil if you want! There's nothing wrong with switching back and forth between the two either. As long as the oil meets all the specifications set forth by the manufacturer...

A synthetic oil doesn't lube any better than a dino oil for the first 3000 miles. After that the dino oil starts losing many of it's TBN's (Total Base Number a.k.a. a measurement of the amount of active additive left in a sample of oil) which is where the synthetic oils have the advantage. They retain their respective TBN's longer than a dino oil and thusly can be pushed farther between oil changes.

U.M.
 
midlifecrisis99cobra said:
Whether it lubes any better or not I'd consider up for debate. It will keep the engine cleaner as it has much less tendency to coke. My memory is that it does lube better on cold starts. Maybe someone else can help here.
So why would a 10W30 synthetic lube better than a 10W30 dino oil? They both have the same weight in the cold (10)? :shrug:

U.M.
 
It's supposed to cling to the engine surfaces better, if I remember correctly. In other words, the crank and cam bearings, along with everything else for that matter, wouldn't start out as dry as they would with dino oil. Don't know if this is true, but that's the claim.
 
I've also heard some people say that after a certain amount of miles on the car, its not good to switch to Synthetic Oil. I was thinking of switching the car to synthetic next around but i have about 45k miles. Should i simply stick with the conventional?

Also, same question for the synthetic transmission fluid. Is it okay to switch after 45k miles?
 
HoustonGT said:
I've also heard some people say that after a certain amount of miles on the car, its not good to switch to Synthetic Oil. I was thinking of switching the car to synthetic next around but i have about 45k miles. Should i simply stick with the conventional?

Also, same question for the synthetic transmission fluid. Is it okay to switch after 45k miles?
Urban Legend.

U.M.
 
I've been running Mobil 1 synthetic since I bought my car with 23K on it 3 years ago- I've been changing oil and filter every 5-6k miles, now at 61K miles-

Do you guys think that this is being overly conservative? I've heard synthetic can go quite a bit longer safely. For those of you out there running sythetic, how often do you change?

Thanks, Adam
 
1999SVTVert said:
Do you guys think that this is being overly conservative? I've heard synthetic can go quite a bit longer safely. For those of you out there running sythetic, how often do you change?

Thanks, Adam
I end up changing my oil somewhere between 2500-3500 which truthfully is defeating the purpose for using a synthetic motor oil in the first place. The main reason for switching to a synthetic is its ability to go longer between changes. If you really want to do it right head on over to http://www.blackstone-labs.com/ and request an oil sampling kit from them. Next time you change your oil grab a sample and send it into them. Their kit contains everything you need to catch a clean mid-stream sample... kind of like a urinalysis now that I think about it. :scratch:
Pay a little extra for the TBN testing when you send the sample in. TBN's are the additives in motor oil that keep the engine clean and help keep the viscosity where it should be... amongst a host of other things. Blackstone Labs will send you a detailed report back on your oil telling you everything they find. They will also tell you the condition of the TBN's and whether you can push your car farther between oil changes. They will also suggest oil change intervals based on the test results. (Remember, even though you go 5, 6, or even 10K between changes you'll still want to replace the oil filter and top the oil off every 3K).

I've sent a sample in to them the last two times I changed the oil in my Cobra. I don't ask for the extra TBN test though, I just like to keep an eye on the different levels of iron or silicon in my oil. Here is the report from my last oil sample. As you can see they have alerted me to an increase in the iron content they found. Not a significant increase mind you, but one to keep an eye on.

U.M.
blackstone.webp
 

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