I am replacing the vacuum lines from the intake to the transfer case on my truck. Oreilly did not have 5/32" bulk vacuum hose, but they did have some Prestone windshield washer tubing in 6' sections. I was in a hurry and therefore was an idiot and did not read before making the purchase. I bought 2 6' sections.

Should this stuff be okay to use? My concern is the heat causing it to fail. It has to run down next to the engine/ transmission and back to the transfer case.

Thanks.

is there any markings on the tubing?

No, don't use that you are correct heat may be an issue. Get some nylon tubing and connect with a short piece of rubber hose at each end.
Do not use any old carp, use DOT polyamide 11 stuff, it will last forever. Call these guys.

https://www.freelin-wade.com/nylon-11-DOT-tubing#1

Washer tubing in place of vacuum line - no.

Vacuum line in place of washer tubing - sure.

For either, you can get a 10ft roll of silicone on eBay for like $6.

Just curious what the rubber at the end would do? Is this just not as flexible as silicone/ rubber?

The windshield washer tube hose will work fine until it sees vacuum and collapses. No it is the wrong application.

This is the first thing that came to my mind.

Same here, the two types of hose are made to handle opposite types of pressure. I may not worry so much about the under hood temps (since the washer hose should be designed to handle the same environment), but I wouldn't want the hose to collapse under vacuum.

As with nylon there are many types and grades, on my VW every vacuum hose is thick wall silicone, its works great, not cracks, resist heat, stays flexible at extreme cold temps doesn't loose it pliability, etc.

http://www.hps-siliconehoses.com/hps-silicone-vacuum-hoses-silicon-tubing.html

Make it once with the best materials and it will be better than OE and you can forget that issue for many many years or decades.

When the steel vacuum lines to the front axle on the Grand Wags rotted. I replaced it with a length of hose that was cable tied to the fender. Not run underneath the ex manifold. I am liberal when I replace factory wiring/plumbing because factory is clotheslined to the mm. Granted it is 24 yrs old, but the wiring on the Rat is shrinking as the jackets on wiring harden. It shrinks away from the ends and exposes stressed copper strands to the elements. They either turn green and break, or just break.

I don't think windshield washer tubing can withstand any pressure/vacuum, may be at the lower end but how much?
It is mainly a regular water tubing.

The vacuum tubing is a vacuum/pressure tube made to withstand vacuum/pressure.
The pressure in a car vacuum system is actually high, don't recall how high but it may be more than a windshield washer tubing can handle.

The AC system, brake fluid system, power steering, transmission system and fuel system have even higher pressure potentially plus need the ability to withstand the appropriate fluid passing through it.
Those lines/tubing are made using special crimp with high pressure hoses and threaded fittings.

I went for "bold & beautiful blue".

I was going to buy 20' of hose but they want $26.xx for shipping. That's the cheapest option.

I realize silicone is better than rubber.. I was just trying to buy everything local to speed things up a bit.