Would you convert your Steet Rod 350 SBC to synthetic oil ?

[Learpilot]

Would you convert your Street rod Small Block 350 with 25000 miles to synthetic oil ? Is there a lot of difference between full synthetic and a blend ?
I drive about 3000 miles a year mostly going to car shows on weekends.
Also how often do you change your oil ?
Thanks , Rick

[Fat Cat]

I have converted all my cars to synthetic. My daily driver has been running synthetic for about 40,000 miles. I change the oil about every 9 months which works out to about every 8,000 miles. My Dakota has not had an oil change in nearly 18 month but in that timeframe I have only driven it about 3,500 miles. I have been using Mobil-1 Synthetic Extended service oil which has a 15,000 mile service life.

When my 47 Chevy hits the road it will have standard oil in it for the first 3-4,000 miles and then it will be transistioned to synthetic.

When I did the conversion on my daily and the truck, I changed from standard oil to a synth blend. I also moved the change interval from 3,000 to 4,500 miles. Once I finally changed to full synthetic I changed to a 10,000 mile change interval but that was close to once a year for the daily and the oil looked much worse than when I change it at 8,000 miles. I have theorized that because I only drive 16 miles round trip to work every day that that last 2,000 miles on the oil was when most of the change from normal looking synthetic oil to the look of standard oil at 3,000 was occuring. At 8,000 mile change intervals the oil still looks almost like new.

[Carnut]

I've been running synthetic in just about everything I have.

I've been using synthetic since the late 70's when it first became popular.

Started out with a brand that was touted in popsci mag in competition to amzoil at the time. Heh, heh, don't remember the name.

But that was the first synthetic I put in my 67 Dodge Charger at the time.

All the cars I bought and engines I built after the late 70's have has synthetic in them.

When Pennzoil came out with their synthetic PZL, I used it in my Charger and my coupe and several other rides.

When PZL became scarce I switched over to Mobil 1. I had avoided Mobil 1 originally because it was a 'different' type of synthetic and wasn't exactly considered a true synthetic, but it the other the other brands I had used just became too scarce. I just didn't want to wind up in west podunk and need more oil than I could carry with me.

So, since then, about 85 or so all my cars have used Mobil 1, I've never been concerned about the mileage on the vehicles at time of conversion and haven't had any problems that I know of. I did notice that synthetics tend to find leaks easier than other oils on some used engines.

I'm still running synthetic in my 67 Dodge Charger w/49k mi on it. Back in 90 or so, I replaced the clutch and had the 4spd tranny gone thru and when I put it back together I put in Mobil 1 Synthetic 90 Wt Gear lube in both the trans and the rear end. Not real sure if it helps or not, but that's what I am using.

I also have used Mobil 1 ATF in my new 91 Grand Am when I had it and never had any problems with it that I am aware of.

SInce both my 40 and my 61 Chrysler Auto trans leak, I haven't put any of the Mobil 1 ATF in them.

What really got me on synthetics was when I was riding a Honda 360 to work every day about 15mi each way, bought the bike brand new and for the first 15k mi or so on regular oil, then converted over to my first synthetic at the time and the mileage went from an avg of 45mpg to an avg of 50mpg with not other changes, that kinda sold me on synthetics.

So on the conversion of higher mileage engines to synthetic, I"ve done it on several and have had no problems except for some more noticeable leakage on gaskets.

I've always changed my synthetic oils at 5K mi no matter how long it takes.

[taxpyer]

The main consideration for me is cost versus benefit. Up here, Royal purple is $13 / L .  I have it in my '47 jeep engine (80's vintage) and it seems fine but I'm not sure of the benefits, if any. I know that the motor was not designed for it and so I wonder if the tolerances in it are enough to really take advantage of it. (I bet Wayne could inform us abit on that)
I totally agree with fatcat (who gave a very good break down of synthetic by the way) it does like to find where it can leak.
Synthetic gear oil might prove to be the most beneficial. I know for sure that synthetic gear oil in large truck trans and diffs will lower operating temps by a substantial amount.  
I'm going to take it out of my jeep mainly because I want to change my oil more often (seasonal)  and so I don't really see the cost/benefit of it at this point being as my mileage is quite low each year.
Now if I had a new Mustang or something like that I think that it would be a perfect match to use synthetic in it.
The oils made today are far superior than the oils of 20 years ago, so with that in mind the stuff off the shelf is a pretty good product to trust in your car and you can always add a good additive like the product GM puts out for that extra piece of mind.
I also use gas stabilizer in my seasonal cars because of the poor storage qualities that ethanol has.

anyways just a thought

[Carnut]

I'll also add a comment on synthetic conversion.

I've found that viscosity of synthetic is generally less than regular oils.

Like a 10w30 regular oil in a SBC might show 30lbs pressure at idle when I converted to the similar grade 5w30 synthetic the pressure would drop to 20/25lbs.

So I tend to run the highest viscosity I could find. I have been running  20
15w50 whenever I can find it and I tend to search for it before buying.

So far the higher viscosity I've used hasn't hurt anything, but I read a great deal about synthetics in the early days on the theories and it was said the lower viscosity was ok and still resulted in less friction and better gas mileage. But my backyard theorizing still has me using higher viscosity to maintain oil pressure.

Heh,heh, when Corvettes started coming from the factory with Mobil 1 in them it kinda sealed the deal for me.

Also be careful the Mobil 1 brand name has now been spread around to several versions of Mobiloil and I don't think all of them are synthetic anymore.

[Learpilot]

THANKS you all answered all my concerns. Thanks for the tip about lower oil pressure. You said Corvettes come from the factory with Mobil 1 oil. Mercedes also uses Mobil 1 in all there cars. I have a friend that is a mechanic at the local Mercedes dealer. He said that it is not good to start with a new engine with synthetic because the rings need to wear in to get good compression. He has some cars that use oil and he thinks it is from starting out with synthetic oil. He takes the cars out and runs them in 1st gear at 5000 rpm for a few minutes and that take care of the burning oil.

I think I will convert to synthetic blend for the first oil change then the next oil change go full synthetic.
THANKS Again , Rick

[Crosley.In.AZ]

I would be concerned about the flat tappet camshaft going round.

[slocrow]

Interesting! I believe synthetic is better but can't be run across the board. I've found that for the most part you're better off with synthetic, if for no other reason then you (the changer) do the labor ½ as much. With such limited miles as I put on the 32 I just use the dyno stuff. I tried synthetic in the L98/91 Corvette for about 5 years and then while getting some work done, had the oil changed. They used dyno Castrol. Guess what? All those little oil leaks I was getting for the last 5 years are now history. I don't know but I had previously heard that the thin (?) synthetic will slip by the seals and gaskets some. I ignored it as old wives tails but it did happen to me so a word to the wise.
I use synthetic in all my daily drivers along with the extended family cars, which I change the oil in. Back to that labor thingy.
I change depending on useage. Syn every 7-9M and dyno every 4-5M ....Frank
PS: I think Corvettes started in 92 with the LT1. And you are speaking about conversion not new break-in, correct?