027 and o gauge cars

Yes & no. Depending on which trains.

Basically true 027 scale from Lionel and Kline were smaller & considered more toy like. Those I would not put in any o gauge consist.

However MTH rail King trains are a larger scale. In fact there are two scale sizes among the line. A medium and large so to speak. With the ones mentioned above being smaller.

Now that said, in real life there are larger freight and smaller freight cars. Which makes it able to mix some of the larger MTH rail King cars with MTH premier cars. 

Allan,  The first and great rule of our hobby is, "It is your layout, you may do whatever you want."  If you like running O and O27 cars in the same train, do it.  If you like running a passenger car in a freight train or a freight car in a passenger train, do it. It is your money, your cars, your layout.  There is no Omni-present panel to make judgment on how you relax and enjoy your hobby.   John

It would depend on whether the size difference bothers YOU, to a degree, even during any particular era, there was/is different sizes of similar cars, so in that regards, it depends on what you can live with.

Mechanically, there should be no reason why you couldn't mix 027 and O Gauge rolling stock, if the curves are sufficient for the O Gauge cars, the 027 cars will run on any track that the O Gauge cars can run on. The only other consideration that I can think of would be car weight. Too many light weight cars ahead of too many heavy cars in a long train can "String Line" on curves, pulling the lighter cars off the track to the inside of the curve, but that is a WEIGHT issue, not 027/O Gauge, 027 cars just tend to be lighter than O Gauge cars typically.

Do What YOU Like, Trains are Supposed to be FUN,

Doug

Many Thanks Gents, Gentlemen.... and I guess I do use THAT term loooo-sely, as I check over my shoulder for the "Rubber chicken launcher and Girraffe herd"

Allan,

Mix and run what looks good to you. I run what looks good to me from 5 to 10 feet away. For example, my preference is steam era passenger trains, so I run a scale N&W J 4-8-4 with a consist of 7 MTH Rail King 13-inch long passenger cars. This train is close to 10 feet long, but it looks realistic from 5 to 10 feet away.

I regularly mix "traditional" size cars with ones that are scale.  If you watch a real manifest freight train, you'll see quite a bit of disparity in car size so; why not do the same on your model railroad?

Curt

If you look at some older films of freight trains, you might notice how varied in size the cars can be.  Particularly in the period when wood sided cars were still being used along with newer steel freight cars.  

In the "old days" , there was the O Gauge line and O27 line, yet even Lionel blurred those lines. In some cases, they offered the same engine in both lines with a different number. The 4-6-4 Hudson was numbered 646 in O Gauge and 2046/2056 in O27. Same engine. Similarly, the iconic O Gauge Santa Fe and NYC F3s were offered in freight sets with O27 rolling stock.

Today, the lines seem to be drawn between scale and traditional or non-scale (or semi-scale, but that term draws out the grammar police). Scale at 1:48 tend to be larger item for item than traditional (scale Berkshires are bigger than traditional Berkshires, etc.). But a small in real-life engine, such as 0-4-0 or 44-Tonner switchers, can look at home with on a layout with mostly traditional equipment. My brother-in-law's scale Mountain looks silly with my traditional items, but his scale 2-8-0 looks fine.

So, I guess that answer is, "it depends." 

I routinely mix 1/4" scale and 17/64" scale - the latter is correct for O gauge track.

I agree - do what makes you happy.