warrrreagl

I have an '89 Chevrolet pick-up that I rarely drive. It's mostly just a glorified wheelbarrow. The last oil change it got was February of 2004, and since then it has only been driven 2000 miles.

I took it to get an oil change this week and the mechanic tried to tell me that the color of the oil was as if brand new and he didn't think it needed an oil change. I told him it had been over a year since the last oil change, but he kept saying it didn't need one.

I finally had to get his boss to MAKE him give me an oil change.

I've never had a mechanic tell me something didn't need doing. What are your thoughts? Can oil viscosity break down over time even if the vehicle sits without driving? Do you think the mechanic was right?

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twilightfoix

yes the mechanic was right, oil will break down over time but if you only drove it 2000 miles in a year it very well quite possible that you didn't need an oil change

cyrnel

Depends on the engine and the 2000 miles. Carbureted or fuel injected? If the pickup has only driven bunches of short, cold start trips then even a good synthetic could be in trouble dealing with all the condensation & fuel dilution. On the other hand, if you burned off contaminants once a week with 15minute drives then the oil might have been in great shape.

Don't give visual inspection much weight. Fuel or water contamination will wipe out the additive package without doing much to the appearance. You can also have the smallest amount of soot contamination that makes oil look terrible when it still has 10K miles left.

Each engine with its set of operating circumstances is unique. If it were mine, and more important than a wheelbarrow, I'd have a single end-of-season oil analysis done to see how the workload/storage routine is affecting the oil. That'll let you guide future changes based on chemistry instead of rules-of-thumb that break down with unusual workloads.

Consider using a diesel engine oil. The additive packages are much stronger than provided by just about any gasolne oil so they hold up to contaminants from oddball miles proportionally longer. Or, drain a little and top up with a fresh quart every six months. More than likely you'll be safe going out to 2yrs if you replenish it this way. Still though, no way to know without the analysis or if you begin to see effects of pushing too far.

Nimisys

most manufactors reccomend once a year, even with thier new fangled oil life monitoring systems. i am not sure with regular dino oil if i would push past year oil, even with 2000miles on it.

MSD

The problem with time is that crankcase blow-by gasses accumulate in your oil and it starts to become acidic. It may look perfect, but it's slowly eating your engine.

One a side note: I work at an oil-change shop, and I laughed at the idea of someone telling you that you didn't need a service performed that you wanted. We'll push stuff at you if there's so much as a speck of dust in fluids, especially if it's beyond the reccommended service interval.

cyrnel

Blowby consists of combustion byproducts (soot, water,...), unburnt fuel, and engine wear material, with soot (the black stringy part of dirty oil) being the greatest contributor in a healthy engine. If blowby were an issue in this engine at those miles then the oil wouldn't appear new. There could be other contaminants seriously messing up the chemistry but problem blowby is very visible.

If there's fuel or water contamination it wouldn't necessarily be visible. A leaky injector or poorly operating carb can dump lots of fuel. Lots of cold starts and no highway running can add lots of water. By 2000miles it may have used up the add package and the oil could easily be out of viscosity range even if it looks & smells fine. Delo 400 or similar "C" diesel oils handle these situations well but the average dino SL rated oil would probably be dead.

Bottom line, it depends.

Agreed. The guy was either stubborn or unusually ethical.

Edit: typo from hell

RaDiAn

Is it garage kept?

Do they make any additives that you could dump in to reduce and or rebalance the chemistry or lower acidic levels?

I have Blazer that I only drive in the winter and or if other car is broken down. So it sits for a while in between drives. I didn't even think about the oil sitting so long.

cyrnel

Retailers set aside lots of space for aftermarket additives. It's a big industry with large margins. Most of these products are 90%+ common commodity basestock plus solvent with an overload of one or another "special feature" additives, sold at a premium. They can help in the few areas they reinforce but might not be what you need. They can also interact with your existing oil in ways that aren't good. Viscosity changes out of range, TBN drop, even components that'll increase acidity. Don't play garage chemist. You'll have more predictable luck topping up with a fresh quart of the same oil you're using now. If that means draining or pulling a quart from the dipstick tube, do it. If the vehicle has been sitting, exchange the quart then drive at operating temp for 20minutes. The fresh quart will bring back the additive package and the driving will burn off water and any unburnt fuel that breaks it down.

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