Hi all, is it true that robusta blends are oilier and has more fat content thus it will cause me to have my grinder burrs clean more frequently? will robusta blends dirty my espresso machines and grinder and shorten their lifespan?

dark roasted beans have lots more oil. Whether they are robusta or arabica.

No, I don't think so. Besides, most robusta 'blends' don't have much robusta in them anyway, just a few percent to boost crema and caffeine a bit. I'm not sure about pure robusta though as I have not roasted a pure robusta in years. I don't recall it causing any problem in the roaster, grinder or machine...plenty of crema though, so there must be somewhat more coffee oil.

I think all dark roasted beans tend to produce more oily, especially after 3 days post roasting.

Hi all, is it true that robusta blends are oilier and has more fat content thus it will cause me to have my grinder burrs clean more frequently? will robusta blends dirty my espresso machines and grinder and shorten their lifespan?

It may appear like robusta beans are more oily than Arabica beans due to the enhanced crema formation, but the opposite is true: In general robusta beans contain less oil than arabica beans. The crema on robusta beans has a slower rate of dissipation due to the lower oil content. I have read this on a few occasions, but this is the link that I could readily trace:

http://www.google.nl/url?sa=t&rct=j&q=& ... 2taRaJOMsg

(Similarly, you can argue that semi-skimmed milk produces a more steady froth than whole milk, because the rate at which the air bubbles are drained is slower.)

It depends on the roast profile how oily the bean looks on the outer surface. When I was using a super automatic machine, I was once given a 0.5 pound bag of very dark roasted beans with a very oil-shiny surface. When I tried them, the spent grinds did not come out as the usual loosely tamped pucks, but as a sludge. Also before the bag was spent, the grinder motor had failed.
A (semi) commercial grade grinder should not have any problems with either robusta beans or dark roasted beans of either variety. The manual of my Compak grinder however does advise a more frequent cleaning cycle if dark roasted beans are used.