My oil light blinks when I’m at idle (<1000 RPM) and the engine has warmed up. I have plenty of oil, according to dipstick checks. Nothing sounds amiss, no knocking, no rough idle, no other warnings.
I have an idea that it might have something to do with oil pressure, but I don’t know enough to be able to diagnose it beyond that. I’d just as soon not spend a lot of money that I don’t have by taking it to the garage. Sound like something I can check myself, and maybe fix?
The manual calls for 20/50 oil. There have been cases with the Mark III Golf/Jetta 2.0 (2slow) engine with using lighter weight oils, and the oil light flashing. Something about pressure, but I don’t remember what exactly the details were. Click & Clack didn’t believe the car could possibly call for oil that thick, but it’s in the manual, and I’ve read some posts about this exact problem.
If you brought it to a garage of any type for a change they may have put 5-30 or 10-30 oil in it, and this can cause the problem.
A good site VWVortex.com has a good message board for the “dub heads” out there. They’ve been great for me (most of the time), and may be able to give you a more focused opinion.
-Butler
When was the last time you replaced the oil filter? That might not be it, but it would be my first step.
What butler mentioned was my first thought too. Most Volkswagen engines call for higher viscosity oil than what can normally be used in other makes of cars. I usually use 15W-40 or higher (the manual gives several options depending on expected temerature range). It’s not unusual for the oil light to come on sometimes if lower viscosity oil is used.
Most quick-lube places, a lot of independent shops, and even a few dealerships put 10W-30 in everything. If you don’t know what viscosity oil is in it now, the logical first thing to do is change it and make sure the right stuff goes into it.
If the light still flashes at idle with the right oil in it, the next thing to try is replacing the oil sending unit(s). Relatively cheap and easy, and a reasonable probability it might fix it. If the light comes on after that is done, it’s time to have the oil pressure tested at a knowledgeable shop (make sure they’re familiar with this aspect of VW engines).
I bring my brother in law a bottle of Jack Daniels, and he does work on my cars. I live on a hill with no garage, while he has a flat driveway and a garage. We last changed the oil and filter in late December, early January. Actually, we redid the gasket on the oil pan then, looking to stop a small leak, so we just changed everything. We’ve been changing it ourselves for the past year, when I inherited the car. We use 10-30 oil. I used a quick-lube once in that period, back in May. The problem didn’t surface until yesterday.
I basically just use the car to go to work (less than 10 min away) and running errands. Long drives with the family are done in my wife’s car, because the child seat is there.
I don’t know where the manual is, and the local auto part store didn’t have a Chilton’s the last time I looked. Someone else had mentioned the sending unit, but I don’t know where it’s located. I’ve been told it’s a <$10 part. Do I have to drain the oil when I replace it? I probably will anyway (using 15-40 or higher this time, per your suggestion), but I’m curious if it’s necessary.
Am I doing damage by still driving it, or do I have to ground the car until the weekend when I can get it fixed?
I’d still change the oil first and see what that does. If that solves the problem, you’re done.
There’s no need to drain the oil to replace the oil sending unit. Oil senders are often installed in the oil filter housing or in the block somewhat close to the oil filter, but sometimes they’re located elsewhere. Older VW 4-cylinders had two oil senders, one on the filter housing and one on the back of the cylinder head. I don’t know where it (or they) would be on your engine, unfortunately. Usually if you have the new sender to look at, you can find the old one by searching along the engine for the part that looks like it.
If the light is just flickering at idle, I doubt it’s doing any real damage in the short term. A few more days of gentle driving is unlikely to make a difference.
Now that’s some right fair payment!!! 
Don’t go for the Chiltons for the VW, go for the Bentley manual.
Good luck!
-Butler
98 VW Golf. 188K miles.
$65 vs ~ $20 for a Chilton’s? Is it really that good, or is a Chilton’s for a VW that bad? I’ve had Chiltons for all my cars in the past. They were all American made, though, and mostly GMs.
I actually bought one for my mom’s previous VW, a 91 Golf, I think. I forget what I needed it for, but I don’t recall it coming up short in the info department.
I had this problem with several older VWs, it turned out not to be a problem at all. The issue is oil pressure, when you idle down the oil pressure dips just barely enough to trip the warning light. Does the Jetta have a separate oil pressure gage? Look there and you’ll see that it’s right around the level that trips the warning light (which I can’t remember ATM). As long as a light tap on the accelerator causes it to stop blinking, you should be fine. (At least I was, and my mechanic agreed) It never happens in my current '97 Cabrio, and I’m at 150K (and planning to change the oil tomorrow, strangely enough )
The Bentley is much bigger, and IMO much more complete. I also just linked to the publisher’s site, as that was easier for me, you can find it for much less of course.
I went with the Bentley after seeing similar discussions on the merits of both on the vwvortex.com site I referenced in post #2.
I’m sure the Chiltons is fine for a casual backyard mechanic, but the Bently has diagrams of darn near every system. And the VAG (computer) codes.
It’s more than paid for itself in my garage.
-butler
The Bentley manuals I’ve seen included both the owner’s manual and the factory repair manual. Reprinted by Bentley, of course, but word for word and picture for picture what was in the originals. Excellent books.