I’ve been thinking about how to best maximize return on the big Delta partner promotion I wrote about yesterday, offering up to a 150% bonus on most partner miles through the end of the year.

Last night I transferred a bunch of Diners Club points. Diners Club is offering up to a 35% transfer bonus to begin with, which on its own wasn’t enough to entice me. That offer runs through the end of the year and is tiered as follows:

-Transfer 10,000 to 19,999 points and receive a 15% mileage bonus
-Transfer 20,000 to 29,999 points and receive a 25% mileage bonus
-Transfer 30,000 or more points and receive a 35% mileage bonus

But on top of that 35% bonus, Delta will give me another 150% bonus. As I said before, I’m not a fan of Skymiles in terms of their relative value mile-for-mile with most other airline programs. But when the bonuses are this huge it more than makes up for the difference. (Sadly, while Diners Club transfers qualify, American Express Membership Rewards transfers do not.)

Frugal Travel Guy suggests a Budget rental car promo:

From there, using coupon code MUAZ025 rent cards from Budget again on their one day with Garmin Where2 GPS system. the promo pays 5K Delta miles for a one day rental.

Here is my math; 5K + 7.5K (150% bonus) =12.5K Delta miles per rental. I came up with about $55 including the GPS system on Hilton Head and about $50 in Traverse City.

That sounds to me like $100 to $110 per 25K Delta miles or about $.0044 per mile, when you pass the 10K transfer threshold.

Details on the promo, valid at participating airport locations, can be found here.

Frugal Travel Guy wants folks to get to 10,000 Delta partner miles first, before doing the Budget promo, but it’s not clear to me why this would be necessary — as long as you hit at least 10,000 miles in partner activity total during the promo for example by doing the Budget promo twice. Then you hit your 10,000 mile threshold and qualify for the full 150% bonus on all partner activity earned even if you don’t have any other activity at all.

The only worry I’d have is if they post the ‘regular’ partner points from the Budget promotion as base and the 5000 bonus as ‘bonus’ and if — though this certainly isn’t spelled out in the promo terms and conditions — they decide that bonus transactions aren’t bonused in the promo. That’s the one scary piece.

Last month Delta offered a 100% bonus on points transferred from one account to another. That was enough for some, not enough for others. 30,000 points are transferred at a cost of $330. Now this promo yields a 150% bonus instead, so you and a friend can each transfer 30,000 miles to each other and wind up 45,000 miles ahead for $330. Each account can receive up to 300,000 miles per year and transfer out 150,000 miles per year.

The promo sure makes the Delta Amex the best credit card to put pretty much most spending right now, as long as you’re hitting 10k in the promo overall you’re earning 2.5 miles per dollar spent which is pretty huge.

I with I knew whether they would bonus all or part of the Delta Americen Express signup bonus for new cardmembers, though. The terms and conditions of the offer do say they’re bonusing points earned via spending on the card, it’s unclear whether the bonuses are coded as spending or otherwise (only unclear because I haven’t researched it!) though I would make the case that the bonuses come only as the result of purchases, that is you can’t just apply and not spend money on the card at all and still get the bonus. The bonus results from card spending so I’d sure fight for it to be eligible though they could tell me where I could go….

I also like 62.5 miles per dollar spent at FTD (25 miles per dollar + 150% bonus). 1-800-Flowers has the same earn ratio using promo code DL28 but I trust them to post the miles properly a whole lot less than I do FTD.