I have a ticking noise in my 94 MPV that has been annoying me for the last 160,000 miles. I have now 198,000 miles on and I am finally sick of it. Hot or cold, varies with engine speed, comes and goes, may tick for 20 minutes at 60mph then quits for 10-20 minutes then starts again. Doesnt effect gas mileage or operation. Can anybody help???

The noise problem is 90% chance in your valve lifters.

What will fix your problem is use only a Mazda oil filter.

or in the alternative,

Use the smallest possible oil filter you can find that will work with your vehicle.
FYI, the Mazda oil filter will fix your problem simply because it has an anti-drain valve inside that prevents the oil from the lifters from running backwords in to the motor.
Tiny oil filters will also improve the situation because they will fill up will oil very fast when you first start the motor.
You see, people don't seem to understand this, but you always need the smallest oil filter you can get, instead of a large one because the motor doesn't have to run dry of oil for a few mili-seconds everytime the motor starts. (People usually want to use the larger ones because they think they clean the oil better)
Trust me on this, dirty oil doesn't do near the damage that NO oil for a mili-second does.
Finally, let me explain why your lifters knock sometimes and sometimes "NOT".
.......The lifters have very tiny pores (holes) in the top, that fill up with oil.
Oil can come out of them easily, but it is a very slow and difficult process for the motor to fill them back up with oil.
If everything is in the right spot and the oil filter does not allow the oil to drain backwords, then NO noise.
If the motor and oil filter gets in a bad position such as setting too long, etc. then the oil drains out of the lifters and takes much time to "PUMP" themselves back up.

Hope this helps.

You have a very common Mazda problem. I went through this phase with my 88 626. The previous post is right on the money. Use the best quality oil filter you can get; Mazda, Bosch. Change your oil as often as possible. Dirty oil/long oil change intervals bugger up the HLA's/lifters. I went to a Bosch filter/synthetic oil for awhile. Problem: if you have a higher mileage Mazda, most of your seals are going to weep and you'll get tiny puddles of oil/oil leaks etc. everywhere.

Now I'm back to regular but good quality 5W30/Bosch filter. Actually I haven't had any ticking for the last 10,000 km cold or hot.