Synthetic oil change interval

[Robert Cain]

Here's a question for all the guys out there using synthetic oils. How often do you change your oil? Should it be changed every 3-5000 miles like conventional oils, or less freqently. Somewhere on this web site, I remember someone saying they changed oil every 20K miles with syntherics. Is this true? I just don't think I have the guts to go that long.

[528HemiDart]

Its less frequent then conventional oil, which I think is about 10k. But it depends what your doing with the vehicle, if its a driver 10k is suitable, but if its a racer, just out of taking car of the vehicle would probly change it every year which would be low miles. A good practise is to remove the oil filter at 5k and pop on a new filter and top off the oil.
Hope I could help

[rumblefish360]

AMSoil has a service. The'll check out your oil. They'll send you a kit and you send them a sample. They check it out and tell ya whats up.
I change my filter in approx. 5-7 thousand. (3 months or so) Total change every 6 months when she was driving the Ford everyday.
Ball game just changed though.
The synth oil is very durable.

[fastmopars .inc]

the reason you must change the oil every 3000miles or 3 months is because of the additives breaking down in the oil.
okay, so the synthetic base oil will remain consistent for probably 10k miles. the additives still are used up at the same rate.
as well, used oil breaks down a lot faster than you would think, and just because you only drove the car 500 miles does not mean that oil can just sit in the crankcase for a year. the carbon deposits in the used oil turn it into an acid over time and it will eat bearings if left for too long.
amsoil is the only oil with an extended service life. they claim 25000 km. (13000miles)
i change my oil every 3 months and have not had a problem.

note : mobil 5w30 was worth .15 of a second over 10W40 castrol non synthetic. roller rockers were only worth 1 tenth.

[mtrv8n]

Yopu change oil when it gets dirty too, and our motors can run a lot of blow-by compared to a tight jap motor in a honda civic. I'd go with 3 months /3000miles..

[superdart]

I ran my Mobile1 Synthetic 5w-30 to 5500 miles. After that is starts to darken real quick, and that's with high end $10 filters.

I just installed the AMSOIL bypass kit on my Ram...She holds an even 8 qts now (plenty of oil for that little 287). I can get another qt if I stepped up to the taller filters, but I don't think that is really needed. I am already convinced that I am going to put one of these kits on my Dart after it is GOOD and broke in.


AMSOIL guarantees their oil to 25K, with proper filter changes of course. They also now have a 7500 mile oil for those that are skittish about running it fir 25K. I am only going to run my oil to 11000, double the Mobile1, but only half the life of the AMSOIL guarantee (oddly enough it will actually be CHEAPER).

[71383bee]

I change the oil every other month which amounts to about 5000 miles on my fiance's daily driver (Olds Alero V6). I think it depends on the filter capacity. The oil could probably go for longer, but the filters can only go to about 5k miles. I feel that if I am under the car switching filters then it just takes 10 more minutes to drain the oil so I change it out. I think your always better off changing oil as often as possible.

[dkn1997]

seems like the "change the oil every 3000" wisdom is always being questioned. If oil changes start costing 50 bucks, maybe I would go longer, but here and now, I can do both daily drivers in my little fleet for less than 20 bucks. I will stick to the 3000. while it may seem to some unnecessary, I have NEVER heard of anyone harming an engine by changing oil/filter everyt 3k. my 2 cents

[71383bee]

I agree, the use of synthetic oil in my book only allows me to maximize the use of the filter. regardless if the oil can take more mileage or not I will change it every 5k. 3k with regular oil. But the synthetic is noticeable because I have gained better fuel mileage and lower operating temps. I don't know about horsepower but i think it is a better product. Changing it every 3 to 5k is just cheap insurance if you ask me.

[amxauto-x]

type of oil makes no differance. as the other guy said the additives and such break down. Change the filter the same tme you change the oil, every 2,000 to 3,000 miles. No exception unless you're racing, offroading, towing all the time.

[mgoudas]

I've been using AMSOIL for 7 years now and change my oil as follows,

Air Cooled tractor; 100hrs 2x briggs recomended of 50 hrs 410 hours on it now.

2.2 5spd shadow; once a year avg. 15,000mi a year this car has 159k on it and runs like a top and burns and leaks NO oil!

4.0L cherokee; once a year avg. 10,000mi a year this one has 163k and leaks a little burns none.

2001 1500 ram 5.2L (My service truck) 45k a year avg. 25,000 between changes 12,500 between filter changes. 61,000 on it now I also run a bypass filter on this truck. These have been hard miles hauling on a lite trip 1000+ lbs all over gods creation and back. Also run the syn. trans fluid in this truck none of the problems that plague these these trucks have come about yet.

The other two run it also but are my backup vehicle and my logging truck probably run less than 2k a year on each so they get BI annual oil changes.

I'm by no means a tree hugger as you can tell by the majority of the of my vehicles. But just think about how much oil we could save if everyone changed their oil only once a year or at 25k!

We could tell the middle east to keep theirs

[superdart]

I just figure that if I CAN run 11,000 between oil changes and still get superior protection, What is it going to hurt? The AMSOIL bypass filter supposedly filters to 1 micron and possibly less...I have met too many people (not working for Amsoil) who run it and have 240,000+ mileson their cars.

I could run to 25K, but I am still leary about that. I figure sionce the filter is up at 12,500, I might as well change the oil too...saves time money, and engine wear.

Technology has progressed, and I firmly believe that longer drain oils are feasible, but the big oil companies are all about volume and money. Think about it, they can make everything else synthetic...Don't you think they could make synthetic gasoline? I bet they already have...but they won't sell it unless the oil starts drying up...

[amxauto-x]

so where do we get info on amsoil that tells us it is so lasting? and other synthetic oil brands? I use Valvoline full synthetic.Is there a study/test that would give viable info on these oils? I'd like to read it if there is any.

I'd heard years ago that amsoil was supposed to be good, but never looked into it. I'm just stubbon I guess. I'd like to learn more.

[dave571]

I don't know anything about amsoil.

I have seen results of lab tests on mobil one, ect.

The results I saw indicated that the main benefit of synthetics were it's extreme temperature durability. Doesn't disintigrate hot, and doesn't turn into tar cold.

It still colects dirt deposits as quickly. And should be changed 3000 miles or 5000km as conventional oils.

I question the benefits of the stuff, in all honesty. I have a 85 gts lebaron turbo, that has had a long life. Just peaked 400000 km. I know it used to burn oil, when it was owned by my sister(dad bought it new in 85)

When I got it in 99, I started to change the oil every 3500km(6 weeks for me). It has not burned a drop of oil since. I use chevron 10w30, out of a bulk drum. The cheapest stuff going, as well as a powerflow oil filter which costs about $3.00 canadian. I ring this car out on a daily basis and have no problems. After I ran synthetic in my van(with 30,000 on a rebuild) it started to drink the stuff. A litre every 150 km. (once a day)

Everybody sees different things.

[amxauto-x]

I still agree with dave571 from ALL I've ever heard. But will keep an open mind and will listen further.

[superdart]

I think alot depends on the vehicle, mileage, when it started getting synthetics.I know that I started putting Mobile1 in my Oldsmobubble at 95k...within 15K it suffered spontaneous catastrophic engine disassembly. The oil blew right out the seals and I screwed up a bearing. Of course, I put some oil in it from our diesel shop to keep the motor quiet, steamed off the motor, nursed it to the dealership, and traded it in on my FIRST new Ram After the deal was done, I let them know that the car was about 5 minutes from death

Hot Rod did an article where they tested a SB Chebby.
They dynoed it, drained all the fossil oils out, and refilled with high end synthetics. After they drove it around the block a few times, they put it back on the dyno, and gained over 30 HP.

This was a 400+ CID SB, and was making over 400 HP to start with.

I feel that there is alot to be gained from synthetics as long it is put in a healthy, freshly broken in engine.

As for the oil getting dirty, the only thing that can cure that is a better oil filter....which there are better ones out there.

[amxauto-x]

Uh oh, filters again! just kidding!

[Dr. Righteous]

Keep in mind that Synthetic oil (100% synth, not blend) is actually liquid polyester. It has little in common with patroleum based oils.
Under the heat and the contamination of blowby patroleum based oil start to break down into its base lower compounds. (gum sludge)
Synthetic oil does not react the same as patroleum based oil. It will get "dirty" from picking up the blow by carbon, and basically cleaning and cooling the engine, but it will not break down into a sludge.
I don't loose any sleep from changing the Mobil 1 5w-40 in my girlfriend's Toyota Camry once a year and a filter change at 6 months with a top off of new oil.
I have used Mobil 1 in vehicles since it came on the market and the next owners reported to me they got 200k miles out of the vehicles before they traded them (or wrecked them) and they didn't use any oil.

[Eternalfootman]

So, can anyone tell me why certain engines seem to just "eat" synthetic oil?

My wifes 4-banger loves synthetic, and will go and go.

My 4-banger will start to "eat" oil at abot 2000 miles. By 3200 or 3500, I'm down a half a quart (disaster when you only have to put in 3.5 qts to fill it). there's no smoke, compression is good, seals are good...

I put Castrol GTX in the same engine, and it doesn't disappear!

What gives?

Dave

[Dr. Righteous]

My dad has a '85 Caddy with a 305. I advised him to switch to Mobil 1 oil because it would be less oil changes throughout the year.
Well his Caddy would 'eat' the synthetic oil as well. Some how the oil got past the rings and was burned. No smoke, or any signs of trouble, but when checking the oil it would be a quart low when it didn't use any on regular oil. He went back to regular oil and left it at that.

[coupe32]

I've got a 340 that has about 7K miles on the rebuild. This engine is in a streetrod. I've always used valvoline oil changing it at 3K miles. Would synthetic oil such as mobil or amsoil be better for the engine? Should I switch to synthetic? I need some opinon on this. Thanks

[Dr. Righteous]

Synthetic oil is much "slicker" than regular oil.
So much so in fact that you cannot use it in a non broken in engine because the rings will never seat.
I have heard that just switching to synthetic oil on a drag car they pick up as much of a 1/10th in the quarter.