I need help

Matt, how many cars?

If they the cars roll freely, then I would think there's either too many of them (but that would probably be A LOT), the traction tires are stretched and they're spinning on the wheels or the oil from the axles is leaking on the track and you're slipping on that.

one of the trains has 5 cars and the other one has ten but i cleaned the wheels after I oiled them too.

Is the engine slipping if it's on the track by itself (no passenger cars)?  If so, the wheels and track need to be cleaned and dried.  I'd use a soft cloth and/or Q-Tips dampened with some Goo-Gone to clean the rail tops and the tread of the wheels.

Does the loco have traction tires?, tires that get oil on them can get slimy to the point its easier to change them than to clean them. If oil isn't the problem, how many cars are you trying to pull and with what locomotive. Passenger cars are typically poor rollers, and in my experince MTH cars do not roll as freely as those from Lionel or K Line. Depending on how many a "bunch" is it just may be too many, not to mention add additional drag when the cars are going around turns. If all the wheels and rails are clean and dry it may be time to shorten the train.

It does have traction tires but I cleaned them willtrythe q tip method maybe it will work hopefully not have to reduce my amount of cars

Matt,

I've used denatured alcohol to clean rubber parts in the past.  As long as you don't soak them in it and dry them afterwards they should be OK.  You could also get some VCR contact cleaner from places like Radio Shack.  They also make cleaning wands.  We used to use this stuff (not Radio Shack but the generic brand of contact cleaner) all the time when I worked on tape drives and such that were on board Navy ships.  The old tape drives had numerous rubber rollers.  The contact cleaner will clean the traction tires, making them grip better.