Please use TRIZOL 

TRIZOL works very well and in case of well-differentiated cells, you will find a lipid layer at the top. You need to pass the tip below the lipid and collect the RNA containing layer. If you couldn't see lipids at the top, avoid collecting the surface layer. May be the amount of lipids is not enough to be seen clearly on the top.

Best wishes. 

You may try Qiagen RNEasy Mini kit. Lipid will be washed from the column by RW1 Buffer. We have been using the same kit to extract RNA from 3T3L1 cells from last few years successfully to extract RNA for Microarray and qRTPCR. 

By using TRIZOL, you could also try RNA extraction using ZYMO RESEARCH (Direct-zol RNA MiniPrep)

We always use TRIZOL for 3T3-L1 RNA extraction. With a previous step well detailed in the protocol lipids appear as a first layer.

Trizol may be a good choice for 3T3-L1 RNA extraction based our experience！

Trizol, you can always transfer the liquid phase (with your RNA) under the lipid phase to a new tube. This way the lipids will not be a problem anymore. 

Hope it helps!

Manual way is working use trizol and check the purity and concentration 

best of luck 

Before, I use Trizol for 3T3L1, it works well!

you may use either Trizol or any commercial kit like Qiazen (if you need high purity).....but the important thing is homogenization and lysis, its crucial for RNA yield.........for homogenization, you may use 20-gauge syringe nidle or homogenization column such as QIAshredder spin column

N.B. if you need small RNA, the use either Trizol or use 'small-RNAs binding column' instead of using normal column.

Maybe Trizol is best for extract RNA from all kind of  tissue .